diff --git a/src/application/ports/file_ports.rs b/src/application/ports/file_ports.rs
index 0d29b645..32ea3355 100644
--- a/src/application/ports/file_ports.rs
+++ b/src/application/ports/file_ports.rs
@@ -119,12 +119,29 @@ pub trait FileRetrievalUseCase: Send + Sync + 'static {
     /// Lists files in a folder
     async fn list_files(&self, folder_id: Option<&str>) -> Result<Vec<FileDto>, DomainError>;
 
+    /// Lists files in a folder, scoped to the authenticated user.
+    ///
+    /// Uses SQL-level `AND user_id` filtering — no in-memory post-filter.
+    /// All user-facing list handlers should use this method.
+    async fn list_files_owned(
+        &self,
+        folder_id: Option<&str>,
+        owner_id: &str,
+    ) -> Result<Vec<FileDto>, DomainError>;
+
     /// Gets file content as a stream (for large files)
     async fn get_file_stream(
         &self,
         id: &str,
     ) -> Result<Box<dyn Stream<Item = Result<Bytes, std::io::Error>> + Send>, DomainError>;
 
+    /// Gets file content as a stream, enforcing that `caller_id` is the owner.
+    async fn get_file_stream_owned(
+        &self,
+        id: &str,
+        caller_id: &str,
+    ) -> Result<Box<dyn Stream<Item = Result<Bytes, std::io::Error>> + Send>, DomainError>;
+
     /// Optimized multi-tier download.
     ///
     /// Internalises: write-behind lookup → content-cache → WebP transcode →
@@ -208,6 +225,24 @@ pub trait FileRetrievalUseCase: Send + Sync + 'static {
             .take(limit as usize)
             .collect())
     }
+
+    /// Like [`list_files_batch`], but scoped to a specific owner.
+    ///
+    /// Used by streaming WebDAV PROPFIND so that each user only sees their
+    /// own files, even in shared folder_id namespaces.
+    async fn list_files_batch_for_owner(
+        &self,
+        folder_id: Option<&str>,
+        owner_id: &str,
+        offset: i64,
+        limit: i64,
+    ) -> Result<Vec<FileDto>, DomainError> {
+        let all = self.list_files_batch(folder_id, offset, limit).await?;
+        Ok(all
+            .into_iter()
+            .filter(|f| f.owner_id.as_deref().map_or(false, |o| o == owner_id))
+            .collect())
+    }
 }
 
 // ─────────────────────────────────────────────────────
@@ -238,6 +273,14 @@ pub trait FileManagementUseCase: Send + Sync + 'static {
         target_folder_id: Option<String>,
     ) -> Result<FileDto, DomainError>;
 
+    /// Copies a file, enforcing that `caller_id` is the owner.
+    async fn copy_file_owned(
+        &self,
+        file_id: &str,
+        caller_id: &str,
+        target_folder_id: Option<String>,
+    ) -> Result<FileDto, DomainError>;
+
     /// Renames a file (system/internal — no ownership check).
     async fn rename_file(&self, file_id: &str, new_name: &str) -> Result<FileDto, DomainError>;
 
@@ -252,6 +295,9 @@ pub trait FileManagementUseCase: Send + Sync + 'static {
     /// Deletes a file (system/internal — no ownership check).
     async fn delete_file(&self, id: &str) -> Result<(), DomainError>;
 
+    /// Deletes a file, enforcing that `caller_id` is the owner.
+    async fn delete_file_owned(&self, id: &str, caller_id: &str) -> Result<(), DomainError>;
+
     /// Smart delete: trash-first with dedup reference cleanup.
     ///
     /// 1. Tries to move to trash (soft delete).
diff --git a/src/application/ports/inbound.rs b/src/application/ports/inbound.rs
index a5ca06f2..2a04da7f 100644
--- a/src/application/ports/inbound.rs
+++ b/src/application/ports/inbound.rs
@@ -16,6 +16,12 @@ pub trait FolderUseCase: Send + Sync + 'static {
     /// Gets a folder by its ID
     async fn get_folder(&self, id: &str) -> Result<FolderDto, DomainError>;
 
+    /// Gets a folder by its ID, enforcing that `caller_id` is the owner.
+    ///
+    /// Returns `NotFound` if the folder does not exist **or** belongs to
+    /// another user.  All user-facing handlers should use this method.
+    async fn get_folder_owned(&self, id: &str, caller_id: &str) -> Result<FolderDto, DomainError>;
+
     /// Gets a folder by its path
     async fn get_folder_by_path(&self, path: &str) -> Result<FolderDto, DomainError>;
 
diff --git a/src/application/ports/storage_ports.rs b/src/application/ports/storage_ports.rs
index 493427c5..045825d5 100644
--- a/src/application/ports/storage_ports.rs
+++ b/src/application/ports/storage_ports.rs
@@ -46,6 +46,22 @@ pub trait FileReadPort: Send + Sync + 'static {
     /// Lists files in a folder.
     async fn list_files(&self, folder_id: Option<&str>) -> Result<Vec<File>, DomainError>;
 
+    /// Lists files in a folder scoped to a specific owner (SQL-level).
+    ///
+    /// Default falls back to `list_files` + in-memory filter.
+    /// Repositories should override with a direct `AND user_id = $N` query.
+    async fn list_files_for_owner(
+        &self,
+        folder_id: Option<&str>,
+        owner_id: &str,
+    ) -> Result<Vec<File>, DomainError> {
+        let all = self.list_files(folder_id).await?;
+        Ok(all
+            .into_iter()
+            .filter(|f| f.owner_id().map_or(false, |o| o == owner_id))
+            .collect())
+    }
+
     /// Gets content as a stream (ideal for large files).
     async fn get_file_stream(
         &self,
@@ -108,6 +124,25 @@ pub trait FileReadPort: Send + Sync + 'static {
         Ok(all.into_iter().skip(start).take(end - start).collect())
     }
 
+    /// Like [`list_files_batch`], but only returns files owned by `owner_id`.
+    ///
+    /// Used by streaming WebDAV PROPFIND to list files scoped to the
+    /// authenticated user, preventing cross-user data leakage.
+    async fn list_files_batch_for_owner(
+        &self,
+        folder_id: Option<&str>,
+        owner_id: &str,
+        offset: i64,
+        limit: i64,
+    ) -> Result<Vec<File>, DomainError> {
+        // Default: filter in-memory (repos should override with SQL)
+        let all = self.list_files_batch(folder_id, offset, limit).await?;
+        Ok(all
+            .into_iter()
+            .filter(|f| f.owner_id().map_or(false, |o| o == owner_id))
+            .collect())
+    }
+
     /// Streams every file in the subtree rooted at `folder_id`.
     ///
     /// Uses an ltree `<@` join against `storage.folders` so the entire
diff --git a/src/application/services/batch_operations.rs b/src/application/services/batch_operations.rs
index 93f03001..9897a581 100644
--- a/src/application/services/batch_operations.rs
+++ b/src/application/services/batch_operations.rs
@@ -117,6 +117,7 @@ impl BatchOperationService {
         &self,
         file_ids: Vec<String>,
         target_folder_id: Option<String>,
+        caller_id: &str,
     ) -> Result<BatchResult<FileDto>, BatchOperationError> {
         info!("Starting batch copy of {} files", file_ids.len());
         let start_time = std::time::Instant::now();
@@ -134,15 +135,17 @@ impl BatchOperationService {
 
         // Arc<str> avoids N heap-clones of the same string
         let target_folder: Option<Arc<str>> = target_folder_id.map(|s| Arc::from(s.as_str()));
+        let caller: Arc<str> = Arc::from(caller_id);
 
         // buffer_unordered materialises only max_concurrent futures at a time
         let mut operation_stream = stream::iter(file_ids.into_iter().map(|file_id| {
             let mgmt = self.file_management.clone();
             let target_folder = target_folder.clone();
+            let caller = caller.clone();
 
             async move {
                 let copy_result = mgmt
-                    .copy_file(&file_id, target_folder.map(|s| s.to_string()))
+                    .copy_file_owned(&file_id, &caller, target_folder.map(|s| s.to_string()))
                     .await;
                 (file_id, copy_result)
             }
@@ -184,6 +187,7 @@ impl BatchOperationService {
         &self,
         file_ids: Vec<String>,
         target_folder_id: Option<String>,
+        caller_id: &str,
     ) -> Result<BatchResult<FileDto>, BatchOperationError> {
         info!("Starting batch move of {} files", file_ids.len());
         let start_time = std::time::Instant::now();
@@ -200,14 +204,16 @@ impl BatchOperationService {
         };
 
         let target_folder: Option<Arc<str>> = target_folder_id.map(|s| Arc::from(s.as_str()));
+        let caller: Arc<str> = Arc::from(caller_id);
 
         let mut operation_stream = stream::iter(file_ids.into_iter().map(|file_id| {
             let mgmt = self.file_management.clone();
             let target_folder = target_folder.clone();
+            let caller = caller.clone();
 
             async move {
                 let move_result = mgmt
-                    .move_file(&file_id, target_folder.map(|s| s.to_string()))
+                    .move_file_owned(&file_id, &caller, target_folder.map(|s| s.to_string()))
                     .await;
                 (file_id, move_result)
             }
@@ -247,6 +253,7 @@ impl BatchOperationService {
     pub async fn delete_files(
         &self,
         file_ids: Vec<String>,
+        caller_id: &str,
     ) -> Result<BatchResult<String>, BatchOperationError> {
         info!("Starting batch deletion of {} files", file_ids.len());
         let start_time = std::time::Instant::now();
@@ -262,11 +269,14 @@ impl BatchOperationService {
         };
 
         // Define the operation to perform for each file
+        let caller: Arc<str> = Arc::from(caller_id);
+
         let mut operation_stream = stream::iter(file_ids.into_iter().map(|file_id| {
             let mgmt = self.file_management.clone();
+            let caller = caller.clone();
 
             async move {
-                let delete_result = mgmt.delete_file(&file_id).await;
+                let delete_result = mgmt.delete_file_owned(&file_id, &caller).await;
                 let id_for_result = file_id.clone();
                 (file_id, delete_result.map(|_| id_for_result))
             }
@@ -307,6 +317,7 @@ impl BatchOperationService {
     pub async fn get_multiple_files(
         &self,
         file_ids: Vec<String>,
+        caller_id: &str,
     ) -> Result<BatchResult<FileDto>, BatchOperationError> {
         info!("Starting batch load of {} files", file_ids.len());
         let start_time = std::time::Instant::now();
@@ -322,11 +333,14 @@ impl BatchOperationService {
         };
 
         // Define the operation to perform for each file
+        let caller: Arc<str> = Arc::from(caller_id);
+
         let mut operation_stream = stream::iter(file_ids.into_iter().map(|file_id| {
             let retrieval = self.file_retrieval.clone();
+            let caller = caller.clone();
 
             async move {
-                let get_result = retrieval.get_file(&file_id).await;
+                let get_result = retrieval.get_file_owned(&file_id, &caller).await;
                 (file_id, get_result)
             }
         }))
@@ -631,6 +645,7 @@ impl BatchOperationService {
         &self,
         file_ids: Vec<String>,
         folder_ids: Vec<String>,
+        caller_id: &str,
     ) -> Result<NamedTempFile, BatchOperationError> {
         info!(
             "Starting batch download: {} files, {} folders",
@@ -650,10 +665,10 @@ impl BatchOperationService {
 
         // ── Add individual files at the root of the ZIP ──────────────────
         for file_id in &file_ids {
-            match self.file_retrieval.get_file(file_id).await {
+            match self.file_retrieval.get_file_owned(file_id, caller_id).await {
                 Ok(file_dto) => {
                     if let Err(e) = self
-                        .add_file_entry_streamed(&mut zip, file_id, &file_dto.name)
+                        .add_file_entry_streamed(&mut zip, file_id, &file_dto.name, caller_id)
                         .await
                     {
                         info!("Could not add file {} to ZIP: {}", file_dto.name, e);
@@ -667,10 +682,10 @@ impl BatchOperationService {
 
         // ── Add folders as sub-trees (bulk subtree queries, not N+1) ─────
         for folder_id in &folder_ids {
-            match self.folder_service.get_folder(folder_id).await {
+            match self.folder_service.get_folder_owned(folder_id, caller_id).await {
                 Ok(root_folder) => {
                     if let Err(e) = self
-                        .add_folder_subtree_to_zip(&mut zip, folder_id, &root_folder)
+                        .add_folder_subtree_to_zip(&mut zip, folder_id, &root_folder, caller_id)
                         .await
                     {
                         info!("Could not add folder {} to ZIP: {}", root_folder.name, e);
@@ -709,6 +724,7 @@ impl BatchOperationService {
         zip: &mut ZipFileWriter<tokio_util::compat::Compat<BufWriter<tokio::fs::File>>>,
         file_id: &str,
         entry_name: &str,
+        caller_id: &str,
     ) -> Result<(), BatchOperationError> {
         let entry = ZipEntryBuilder::new(entry_name.to_string().into(), Compression::Deflate);
         let mut writer = zip
@@ -718,7 +734,7 @@ impl BatchOperationService {
 
         let stream = self
             .file_retrieval
-            .get_file_stream(file_id)
+            .get_file_stream_owned(file_id, caller_id)
             .await
             .map_err(BatchOperationError::Domain)?;
         let mut stream = std::pin::Pin::from(stream);
@@ -749,6 +765,7 @@ impl BatchOperationService {
         zip: &mut ZipFileWriter<tokio_util::compat::Compat<BufWriter<tokio::fs::File>>>,
         folder_id: &str,
         root_folder: &FolderDto,
+        caller_id: &str,
     ) -> Result<(), BatchOperationError> {
         // Bulk-fetch folder tree (small — one entry per folder)
         let all_folders = self
@@ -803,7 +820,7 @@ impl BatchOperationService {
                 for file in files {
                     let file_path = format!("{}{}", zip_dir, file.name);
                     if let Err(e) = self
-                        .add_file_entry_streamed(zip, &file.id, &file_path)
+                        .add_file_entry_streamed(zip, &file.id, &file_path, caller_id)
                         .await
                     {
                         info!("Could not add file {} to ZIP: {}", file.name, e);
@@ -887,6 +904,7 @@ impl BatchOperationService {
     pub async fn create_folders(
         &self,
         folders: Vec<(String, Option<String>)>, // (name, parent_id)
+        caller_id: &str,
     ) -> Result<BatchResult<FolderDto>, BatchOperationError> {
         info!("Starting batch creation of {} folders", folders.len());
         let start_time = std::time::Instant::now();
@@ -902,10 +920,20 @@ impl BatchOperationService {
         };
 
         // Define the operation for each folder
+        let caller: Arc<str> = Arc::from(caller_id);
+
         let mut operation_stream = stream::iter(folders.into_iter().map(|(name, parent_id)| {
             let folder_service = self.folder_service.clone();
+            let caller = caller.clone();
 
             async move {
+                // If a parent is specified, verify the caller owns it
+                if let Some(ref pid) = parent_id {
+                    if let Err(e) = folder_service.get_folder_owned(pid, &caller).await {
+                        let id = format!("{}:{}", name, pid);
+                        return (id, Err(e.into()));
+                    }
+                }
                 let dto = crate::application::dtos::folder_dto::CreateFolderDto {
                     name: name.clone(),
                     parent_id: parent_id.clone(),
@@ -951,6 +979,7 @@ impl BatchOperationService {
     pub async fn get_multiple_folders(
         &self,
         folder_ids: Vec<String>,
+        caller_id: &str,
     ) -> Result<BatchResult<FolderDto>, BatchOperationError> {
         info!("Starting batch load of {} folders", folder_ids.len());
         let start_time = std::time::Instant::now();
@@ -966,11 +995,14 @@ impl BatchOperationService {
         };
 
         // Define the operation for each folder
+        let caller: Arc<str> = Arc::from(caller_id);
+
         let mut operation_stream = stream::iter(folder_ids.into_iter().map(|folder_id| {
             let folder_service = self.folder_service.clone();
+            let caller = caller.clone();
 
             async move {
-                let get_result = folder_service.get_folder(&folder_id).await;
+                let get_result = folder_service.get_folder_owned(&folder_id, &caller).await;
                 (folder_id, get_result)
             }
         }))
diff --git a/src/application/services/file_management_service.rs b/src/application/services/file_management_service.rs
index 07555e7c..e96f861d 100644
--- a/src/application/services/file_management_service.rs
+++ b/src/application/services/file_management_service.rs
@@ -128,6 +128,16 @@ impl FileManagementUseCase for FileManagementService {
         Ok(FileDto::from(copied_file))
     }
 
+    async fn copy_file_owned(
+        &self,
+        file_id: &str,
+        caller_id: &str,
+        target_folder_id: Option<String>,
+    ) -> Result<FileDto, DomainError> {
+        self.verify_owner(file_id, caller_id).await?;
+        self.copy_file(file_id, target_folder_id).await
+    }
+
     async fn rename_file(&self, file_id: &str, new_name: &str) -> Result<FileDto, DomainError> {
         info!("Renaming file with ID: {} to \"{}\"", file_id, new_name);
 
@@ -163,6 +173,11 @@ impl FileManagementUseCase for FileManagementService {
         self.file_repository.delete_file(id).await
     }
 
+    async fn delete_file_owned(&self, id: &str, caller_id: &str) -> Result<(), DomainError> {
+        self.verify_owner(id, caller_id).await?;
+        self.delete_file(id).await
+    }
+
     /// Smart delete: trash-first with dedup reference cleanup.
     ///
     /// Blob ref_count bookkeeping is handled entirely by the PG trigger
diff --git a/src/application/services/file_retrieval_service.rs b/src/application/services/file_retrieval_service.rs
index af641083..d94592fc 100644
--- a/src/application/services/file_retrieval_service.rs
+++ b/src/application/services/file_retrieval_service.rs
@@ -223,6 +223,15 @@ impl FileRetrievalUseCase for FileRetrievalService {
         Ok(files.into_iter().map(FileDto::from).collect())
     }
 
+    async fn list_files_owned(
+        &self,
+        folder_id: Option<&str>,
+        owner_id: &str,
+    ) -> Result<Vec<FileDto>, DomainError> {
+        let files = self.file_read.list_files_for_owner(folder_id, owner_id).await?;
+        Ok(files.into_iter().map(FileDto::from).collect())
+    }
+
     async fn get_file_stream(
         &self,
         id: &str,
@@ -230,6 +239,15 @@ impl FileRetrievalUseCase for FileRetrievalService {
         self.file_read.get_file_stream(id).await
     }
 
+    async fn get_file_stream_owned(
+        &self,
+        id: &str,
+        caller_id: &str,
+    ) -> Result<Box<dyn Stream<Item = Result<Bytes, std::io::Error>> + Send>, DomainError> {
+        self.file_read.verify_file_owner(id, caller_id).await?;
+        self.file_read.get_file_stream(id).await
+    }
+
     /// Multi-tier optimized download.
     async fn get_file_optimized(
         &self,
@@ -311,4 +329,18 @@ impl FileRetrievalUseCase for FileRetrievalService {
             .await?;
         Ok(files.into_iter().map(FileDto::from).collect())
     }
+
+    async fn list_files_batch_for_owner(
+        &self,
+        folder_id: Option<&str>,
+        owner_id: &str,
+        offset: i64,
+        limit: i64,
+    ) -> Result<Vec<FileDto>, DomainError> {
+        let files = self
+            .file_read
+            .list_files_batch_for_owner(folder_id, owner_id, offset, limit)
+            .await?;
+        Ok(files.into_iter().map(FileDto::from).collect())
+    }
 }
diff --git a/src/application/services/folder_service.rs b/src/application/services/folder_service.rs
index 12065275..76ae21a4 100644
--- a/src/application/services/folder_service.rs
+++ b/src/application/services/folder_service.rs
@@ -32,6 +32,10 @@ impl FolderService {
                 Ok(FolderDto::empty())
             }
 
+            async fn get_folder_owned(&self, _id: &str, _caller_id: &str) -> Result<FolderDto, DomainError> {
+                Ok(FolderDto::empty())
+            }
+
             async fn get_folder_by_path(&self, _path: &str) -> Result<FolderDto, DomainError> {
                 Ok(FolderDto::empty())
             }
@@ -196,6 +200,21 @@ impl FolderUseCase for FolderService {
         Ok(FolderDto::from(folder))
     }
 
+    /// Gets a folder by its ID, enforcing that `caller_id` is the owner.
+    async fn get_folder_owned(&self, id: &str, caller_id: &str) -> Result<FolderDto, DomainError> {
+        let folder_dto = self.get_folder(id).await?;
+        if folder_dto.owner_id.as_deref() != Some(caller_id) {
+            tracing::warn!(
+                "get_folder_owned: user '{}' attempted to access folder '{}' owned by '{:?}'",
+                caller_id,
+                id,
+                folder_dto.owner_id
+            );
+            return Err(DomainError::not_found("Folder", id));
+        }
+        Ok(folder_dto)
+    }
+
     /// Gets a folder by its path
     async fn get_folder_by_path(&self, path: &str) -> Result<FolderDto, DomainError> {
         // Convert the string path to StoragePath
diff --git a/src/common/stubs.rs b/src/common/stubs.rs
index b4306839..f25f1c46 100644
--- a/src/common/stubs.rs
+++ b/src/common/stubs.rs
@@ -355,6 +355,10 @@ impl FolderUseCase for StubFolderUseCase {
         Ok(FolderDto::default())
     }
 
+    async fn get_folder_owned(&self, _id: &str, _caller_id: &str) -> Result<FolderDto, DomainError> {
+        Ok(FolderDto::default())
+    }
+
     async fn get_folder_by_path(&self, _path: &str) -> Result<FolderDto, DomainError> {
         Ok(FolderDto::default())
     }
@@ -490,6 +494,14 @@ impl FileRetrievalUseCase for StubFileRetrievalUseCase {
         Ok(Vec::new())
     }
 
+    async fn list_files_owned(
+        &self,
+        _folder_id: Option<&str>,
+        _owner_id: &str,
+    ) -> Result<Vec<FileDto>, DomainError> {
+        Ok(Vec::new())
+    }
+
     async fn get_file_stream(
         &self,
         _id: &str,
@@ -498,6 +510,15 @@ impl FileRetrievalUseCase for StubFileRetrievalUseCase {
         Ok(Box::new(empty_stream))
     }
 
+    async fn get_file_stream_owned(
+        &self,
+        _id: &str,
+        _caller_id: &str,
+    ) -> Result<Box<dyn Stream<Item = Result<Bytes, std::io::Error>> + Send>, DomainError> {
+        let empty_stream = futures::stream::empty::<Result<Bytes, std::io::Error>>();
+        Ok(Box::new(empty_stream))
+    }
+
     async fn get_file_optimized(
         &self,
         _id: &str,
@@ -591,6 +612,15 @@ impl FileManagementUseCase for StubFileManagementUseCase {
         Ok(FileDto::default())
     }
 
+    async fn copy_file_owned(
+        &self,
+        _file_id: &str,
+        _caller_id: &str,
+        _folder_id: Option<String>,
+    ) -> Result<FileDto, DomainError> {
+        Ok(FileDto::default())
+    }
+
     async fn rename_file(&self, _file_id: &str, _new_name: &str) -> Result<FileDto, DomainError> {
         Ok(FileDto::default())
     }
@@ -599,6 +629,10 @@ impl FileManagementUseCase for StubFileManagementUseCase {
         Ok(())
     }
 
+    async fn delete_file_owned(&self, _id: &str, _caller_id: &str) -> Result<(), DomainError> {
+        Ok(())
+    }
+
     async fn delete_with_cleanup(&self, _id: &str, _user_id: &str) -> Result<bool, DomainError> {
         Ok(false)
     }
diff --git a/src/infrastructure/repositories/pg/file_blob_read_repository.rs b/src/infrastructure/repositories/pg/file_blob_read_repository.rs
index 19b9ff7b..f88432e1 100644
--- a/src/infrastructure/repositories/pg/file_blob_read_repository.rs
+++ b/src/infrastructure/repositories/pg/file_blob_read_repository.rs
@@ -260,6 +260,62 @@ impl FileReadPort for FileBlobReadRepository {
             .collect()
     }
 
+    /// User-scoped file listing — adds `AND fi.user_id = $2` to prevent
+    /// cross-user data leakage in the REST API (`list_files_query`).
+    async fn list_files_for_owner(
+        &self,
+        folder_id: Option<&str>,
+        owner_id: &str,
+    ) -> Result<Vec<File>, DomainError> {
+        let rows: Vec<FileRow> = if let Some(fid) = folder_id {
+            sqlx::query_as(
+                r#"
+                SELECT fi.id::text, fi.name, fi.folder_id::text, fo.path,
+                       fi.size, fi.mime_type,
+                       EXTRACT(EPOCH FROM fi.created_at)::bigint,
+                       EXTRACT(EPOCH FROM fi.updated_at)::bigint,
+                       fi.user_id::text
+                  FROM storage.files fi
+                  LEFT JOIN storage.folders fo ON fo.id = fi.folder_id
+                 WHERE fi.folder_id = $1::uuid AND NOT fi.is_trashed
+                   AND fi.user_id = $2
+                 ORDER BY fi.name
+                "#,
+            )
+            .bind(fid)
+            .bind(owner_id)
+            .fetch_all(self.pool.as_ref())
+            .await
+        } else {
+            sqlx::query_as(
+                r#"
+                SELECT fi.id::text, fi.name, fi.folder_id::text, fo.path,
+                       fi.size, fi.mime_type,
+                       EXTRACT(EPOCH FROM fi.created_at)::bigint,
+                       EXTRACT(EPOCH FROM fi.updated_at)::bigint,
+                       fi.user_id::text
+                  FROM storage.files fi
+                  LEFT JOIN storage.folders fo ON fo.id = fi.folder_id
+                 WHERE fi.folder_id IS NULL AND NOT fi.is_trashed
+                   AND fi.user_id = $1
+                 ORDER BY fi.name
+                "#,
+            )
+            .bind(owner_id)
+            .fetch_all(self.pool.as_ref())
+            .await
+        }
+        .map_err(|e| {
+            DomainError::internal_error("FileBlobRead", format!("list_for_owner: {e}"))
+        })?;
+
+        rows.into_iter()
+            .map(|(id, name, fid, fpath, size, mime, ca, ma, uid)| {
+                Self::row_to_file(id, name, fid, fpath, size, mime, ca, ma, uid)
+            })
+            .collect()
+    }
+
     async fn get_blob_hash(&self, file_id: &str) -> Result<String, DomainError> {
         self.resolve_blob_hash(file_id).await
     }
@@ -323,6 +379,70 @@ impl FileReadPort for FileBlobReadRepository {
             .collect()
     }
 
+    /// User-scoped paginated file listing — adds `AND fi.user_id = $4` to
+    /// prevent cross-user data leakage in WebDAV PROPFIND.
+    async fn list_files_batch_for_owner(
+        &self,
+        folder_id: Option<&str>,
+        owner_id: &str,
+        offset: i64,
+        limit: i64,
+    ) -> Result<Vec<File>, DomainError> {
+        let rows: Vec<FileRow> = if let Some(fid) = folder_id {
+            sqlx::query_as(
+                r#"
+                SELECT fi.id::text, fi.name, fi.folder_id::text, fo.path,
+                       fi.size, fi.mime_type,
+                       EXTRACT(EPOCH FROM fi.created_at)::bigint,
+                       EXTRACT(EPOCH FROM fi.updated_at)::bigint,
+                       fi.user_id::text
+                  FROM storage.files fi
+                  LEFT JOIN storage.folders fo ON fo.id = fi.folder_id
+                 WHERE fi.folder_id = $1::uuid AND NOT fi.is_trashed
+                   AND fi.user_id = $4
+                 ORDER BY fi.name
+                 LIMIT $2 OFFSET $3
+                "#,
+            )
+            .bind(fid)
+            .bind(limit)
+            .bind(offset)
+            .bind(owner_id)
+            .fetch_all(self.pool.as_ref())
+            .await
+        } else {
+            sqlx::query_as(
+                r#"
+                SELECT fi.id::text, fi.name, fi.folder_id::text, fo.path,
+                       fi.size, fi.mime_type,
+                       EXTRACT(EPOCH FROM fi.created_at)::bigint,
+                       EXTRACT(EPOCH FROM fi.updated_at)::bigint,
+                       fi.user_id::text
+                  FROM storage.files fi
+                  LEFT JOIN storage.folders fo ON fo.id = fi.folder_id
+                 WHERE fi.folder_id IS NULL AND NOT fi.is_trashed
+                   AND fi.user_id = $3
+                 ORDER BY fi.name
+                 LIMIT $1 OFFSET $2
+                "#,
+            )
+            .bind(limit)
+            .bind(offset)
+            .bind(owner_id)
+            .fetch_all(self.pool.as_ref())
+            .await
+        }
+        .map_err(|e| {
+            DomainError::internal_error("FileBlobRead", format!("list_batch_for_owner: {e}"))
+        })?;
+
+        rows.into_iter()
+            .map(|(id, name, fid, fpath, size, mime, ca, ma, uid)| {
+                Self::row_to_file(id, name, fid, fpath, size, mime, ca, ma, uid)
+            })
+            .collect()
+    }
+
     async fn get_file_stream(
         &self,
         id: &str,
diff --git a/src/infrastructure/services/path_resolver_service.rs b/src/infrastructure/services/path_resolver_service.rs
index ed54e2b2..1eabc457 100644
--- a/src/infrastructure/services/path_resolver_service.rs
+++ b/src/infrastructure/services/path_resolver_service.rs
@@ -32,17 +32,20 @@ impl PathResolverService {
         Self { pool }
     }
 
-    /// Resolve `path` (without leading `/`) to either a folder or a file.
+    /// Resolve `path` to a folder or file **owned by `user_id`**.
     ///
-    /// The query uses `UNION ALL … LIMIT 1`: the folder branch is evaluated
-    /// first, and PG short-circuits if it produces a row.
-    pub async fn resolve_path(&self, path: &str) -> Result<ResolvedResource, DomainError> {
+    /// Adds `AND fo.user_id = $4` / `AND fi.user_id = $4` so that one
+    /// user can never resolve another user's resources.
+    pub async fn resolve_path_for_user(
+        &self,
+        path: &str,
+        user_id: &str,
+    ) -> Result<ResolvedResource, DomainError> {
         let path = path.trim_start_matches('/').trim_end_matches('/');
         if path.is_empty() {
             return Err(DomainError::not_found("Resource", "empty path"));
         }
 
-        // Split into folder_path + filename for the file branch
         let segments: Vec<&str> = path.split('/').filter(|s| !s.is_empty()).collect();
         let filename = segments[segments.len() - 1];
         let folder_path = if segments.len() > 1 {
@@ -51,9 +54,6 @@ impl PathResolverService {
             String::new()
         };
 
-        // Single round-trip: folder branch ∪ file branch, LIMIT 1.
-        // Column order: resource_type, id, name, path, parent_id, user_id,
-        //               created_at, modified_at, size, mime_type, folder_id
         let row = sqlx::query_as::<
             _,
             (
@@ -61,13 +61,13 @@ impl PathResolverService {
                 String,         // id
                 String,         // name
                 String,         // path
-                Option<String>, // parent_id  (folder) / NULL (file)
+                Option<String>, // parent_id
                 Option<String>, // user_id
-                i64,            // created_at epoch
-                i64,            // modified_at epoch
-                Option<i64>,    // size       (NULL for folder)
-                Option<String>, // mime_type  (NULL for folder)
-                Option<String>, // folder_id  (NULL for folder)
+                i64,            // created_at
+                i64,            // modified_at
+                Option<i64>,    // size
+                Option<String>, // mime_type
+                Option<String>, // folder_id
             ),
         >(
             r#"
@@ -87,6 +87,7 @@ impl PathResolverService {
                        NULL::text           AS folder_id
                   FROM storage.folders fo
                  WHERE fo.path = $1 AND NOT fo.is_trashed
+                   AND fo.user_id = $4
 
                 UNION ALL
 
@@ -113,16 +114,18 @@ impl PathResolverService {
                          OR fo.path = $3
                        )
                    AND NOT fi.is_trashed
+                   AND fi.user_id = $4
               ) sub
              LIMIT 1
             "#,
         )
-        .bind(path) // $1 — full path for folder lookup
-        .bind(filename) // $2 — filename for file lookup
-        .bind(&folder_path) // $3 — parent folder path for file lookup
+        .bind(path)          // $1
+        .bind(filename)      // $2
+        .bind(&folder_path)  // $3
+        .bind(user_id)       // $4
         .fetch_optional(self.pool.as_ref())
         .await
-        .map_err(|e| DomainError::internal_error("PathResolver", format!("resolve: {e}")))?
+        .map_err(|e| DomainError::internal_error("PathResolver", format!("resolve_for_user: {e}")))?
         .ok_or_else(|| DomainError::not_found("Resource", path))?;
 
         let (
@@ -131,7 +134,7 @@ impl PathResolverService {
             name,
             res_path,
             parent_id,
-            user_id,
+            uid,
             created_at,
             modified_at,
             size,
@@ -145,7 +148,7 @@ impl PathResolverService {
                 name: name.clone(),
                 path: res_path,
                 parent_id,
-                owner_id: user_id,
+                owner_id: uid,
                 created_at: created_at as u64,
                 modified_at: modified_at as u64,
                 is_root: false,
@@ -169,16 +172,14 @@ impl PathResolverService {
                     icon_special_class: Arc::from(icon_special_class_for(&name, &mime)),
                     category: Arc::from(category_for(&name, &mime)),
                     size_formatted: format_file_size(sz),
-                    owner_id: user_id,
+                    owner_id: uid,
                 }))
             }
         }
     }
 
-    /// Check whether *any* resource (folder or file) exists at the given path.
-    ///
-    /// Equivalent to `resolve_path(…).is_ok()` but avoids constructing the DTO.
-    pub async fn exists(&self, path: &str) -> Result<bool, DomainError> {
+    /// Returns `true` if the resource at `path` belongs to `user_id`.
+    pub async fn exists_for_user(&self, path: &str, user_id: &str) -> Result<bool, DomainError> {
         let path = path.trim_start_matches('/').trim_end_matches('/');
         if path.is_empty() {
             return Ok(false);
@@ -196,7 +197,7 @@ impl PathResolverService {
             r#"
             SELECT EXISTS(
               SELECT 1 FROM storage.folders
-               WHERE path = $1 AND NOT is_trashed
+               WHERE path = $1 AND NOT is_trashed AND user_id = $4
             ) OR EXISTS(
               SELECT 1
                 FROM storage.files fi
@@ -204,15 +205,17 @@ impl PathResolverService {
                WHERE fi.name = $2
                  AND (($3 = '' AND fi.folder_id IS NULL) OR fo.path = $3)
                  AND NOT fi.is_trashed
+                 AND fi.user_id = $4
             )
             "#,
         )
         .bind(path)
         .bind(filename)
         .bind(&folder_path)
+        .bind(user_id)
         .fetch_one(self.pool.as_ref())
         .await
-        .map_err(|e| DomainError::internal_error("PathResolver", format!("exists: {e}")))?;
+        .map_err(|e| DomainError::internal_error("PathResolver", format!("exists_for_user: {e}")))?;
 
         Ok(exists)
     }
diff --git a/src/interfaces/api/handlers/auth_handler.rs b/src/interfaces/api/handlers/auth_handler.rs
index a1413e8d..d44bbb6a 100644
--- a/src/interfaces/api/handlers/auth_handler.rs
+++ b/src/interfaces/api/handlers/auth_handler.rs
@@ -1,7 +1,7 @@
 use axum::{
     Router,
     extract::{Json, Query, State},
-    http::{HeaderMap, StatusCode, header},
+    http::{HeaderMap, StatusCode},
     response::{IntoResponse, Redirect, Response},
     routing::{get, post, put},
 };
@@ -319,26 +319,27 @@ async fn change_password(
 
 async fn logout(
     State(state): State<Arc<AppState>>,
-    headers: HeaderMap,
     CurrentUserId(user_id): CurrentUserId,
+    headers: HeaderMap,
+    body: axum::body::Bytes,
 ) -> Result<Response, AppError> {
     let auth_service = state
         .auth_service
         .as_ref()
         .ok_or_else(|| AppError::internal_error("Authentication service not configured"))?;
 
-    // Obtain the raw access token from Bearer header OR cookie
-    let token = headers
-        .get(header::AUTHORIZATION)
-        .and_then(|v| v.to_str().ok())
-        .and_then(|v| v.strip_prefix("Bearer "))
-        .map(String::from)
-        .or_else(|| cookie_auth::extract_cookie_value(&headers, cookie_auth::ACCESS_COOKIE))
-        .ok_or_else(|| AppError::unauthorized("Authorization token not found"))?;
+    // Extract the REFRESH token (not the access token) so the service can
+    // look up and revoke the correct session.
+    // Strategy: try JSON body first (API clients), then HttpOnly cookie (browsers).
+    let refresh_token = serde_json::from_slice::<RefreshTokenDto>(&body)
+        .ok()
+        .map(|dto| dto.refresh_token)
+        .or_else(|| cookie_auth::extract_cookie_value(&headers, cookie_auth::REFRESH_COOKIE))
+        .ok_or_else(|| AppError::unauthorized("Refresh token required for logout (JSON body or cookie)"))?;
 
     auth_service
         .auth_application_service
-        .logout(&user_id, &token)
+        .logout(&user_id, &refresh_token)
         .await?;
 
     // Clear HttpOnly + CSRF cookies so the browser forgets the session
diff --git a/src/interfaces/api/handlers/batch_handler.rs b/src/interfaces/api/handlers/batch_handler.rs
index 2a0c3da6..f79be065 100644
--- a/src/interfaces/api/handlers/batch_handler.rs
+++ b/src/interfaces/api/handlers/batch_handler.rs
@@ -130,6 +130,7 @@ where
 /// Handler for moving multiple files in batch
 pub async fn move_files_batch(
     State(state): State<BatchHandlerState>,
+    auth_user: AuthUser,
     Json(request): Json<BatchFileOperationRequest>,
 ) -> ApiResult<impl IntoResponse> {
     // Verify there are files to process
@@ -146,7 +147,7 @@ pub async fn move_files_batch(
     // Execute batch operation
     let result = state
         .batch_service
-        .move_files(request.file_ids, request.target_folder_id)
+        .move_files(request.file_ids, request.target_folder_id, &auth_user.id)
         .await
         .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
 
@@ -170,6 +171,7 @@ pub async fn move_files_batch(
 /// Handler for copying multiple files in batch
 pub async fn copy_files_batch(
     State(state): State<BatchHandlerState>,
+    auth_user: AuthUser,
     Json(request): Json<BatchFileOperationRequest>,
 ) -> ApiResult<impl IntoResponse> {
     // Verify there are files to process
@@ -186,7 +188,7 @@ pub async fn copy_files_batch(
     // Execute batch operation
     let result = state
         .batch_service
-        .copy_files(request.file_ids, request.target_folder_id)
+        .copy_files(request.file_ids, request.target_folder_id, &auth_user.id)
         .await
         .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
 
@@ -210,6 +212,7 @@ pub async fn copy_files_batch(
 /// Handler for deleting multiple files in batch
 pub async fn delete_files_batch(
     State(state): State<BatchHandlerState>,
+    auth_user: AuthUser,
     Json(request): Json<BatchFileOperationRequest>,
 ) -> ApiResult<impl IntoResponse> {
     // Verify there are files to process
@@ -226,7 +229,7 @@ pub async fn delete_files_batch(
     // Execute batch operation
     let result = state
         .batch_service
-        .delete_files(request.file_ids)
+        .delete_files(request.file_ids, &auth_user.id)
         .await
         .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
 
@@ -307,6 +310,7 @@ pub async fn delete_folders_batch(
 /// Handler for creating multiple folders in batch
 pub async fn create_folders_batch(
     State(state): State<BatchHandlerState>,
+    auth_user: AuthUser,
     Json(request): Json<BatchCreateFoldersRequest>,
 ) -> ApiResult<impl IntoResponse> {
     // Verify there are folders to process
@@ -330,7 +334,7 @@ pub async fn create_folders_batch(
     // Execute batch operation
     let result = state
         .batch_service
-        .create_folders(folders)
+        .create_folders(folders, &auth_user.id)
         .await
         .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
 
@@ -354,6 +358,7 @@ pub async fn create_folders_batch(
 /// Handler for getting multiple files in batch
 pub async fn get_files_batch(
     State(state): State<BatchHandlerState>,
+    auth_user: AuthUser,
     Json(request): Json<BatchFileOperationRequest>,
 ) -> ApiResult<impl IntoResponse> {
     // Verify there are files to process
@@ -370,7 +375,7 @@ pub async fn get_files_batch(
     // Execute batch operation
     let result = state
         .batch_service
-        .get_multiple_files(request.file_ids)
+        .get_multiple_files(request.file_ids, &auth_user.id)
         .await
         .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
 
@@ -394,6 +399,7 @@ pub async fn get_files_batch(
 /// Handler for getting multiple folders in batch
 pub async fn get_folders_batch(
     State(state): State<BatchHandlerState>,
+    auth_user: AuthUser,
     Json(request): Json<BatchFolderOperationRequest>,
 ) -> ApiResult<impl IntoResponse> {
     // Verify there are folders to process
@@ -410,7 +416,7 @@ pub async fn get_folders_batch(
     // Execute batch operation
     let result = state
         .batch_service
-        .get_multiple_folders(request.folder_ids)
+        .get_multiple_folders(request.folder_ids, &auth_user.id)
         .await
         .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
 
@@ -596,6 +602,7 @@ pub async fn move_folders_batch(
 /// so RAM usage is O(buffer_size) regardless of archive size.
 pub async fn download_batch(
     State(state): State<BatchHandlerState>,
+    auth_user: AuthUser,
     Json(request): Json<BatchDownloadRequest>,
 ) -> Result<Response, (StatusCode, String)> {
     if request.file_ids.is_empty() && request.folder_ids.is_empty() {
@@ -607,7 +614,7 @@ pub async fn download_batch(
 
     let temp_file = state
         .batch_service
-        .download_zip(request.file_ids, request.folder_ids)
+        .download_zip(request.file_ids, request.folder_ids, &auth_user.id)
         .await
         .map_err(|e| (StatusCode::INTERNAL_SERVER_ERROR, e.to_string()))?;
 
diff --git a/src/interfaces/api/handlers/file_handler.rs b/src/interfaces/api/handlers/file_handler.rs
index e011c7c0..1dc43ad9 100644
--- a/src/interfaces/api/handlers/file_handler.rs
+++ b/src/interfaces/api/handlers/file_handler.rs
@@ -632,38 +632,6 @@ impl FileHandler {
         Self::created_json_response(&file).into_response()
     }
 
-    /// Lists files, optionally filtered by folder ID
-    pub async fn list_files(
-        State(state): State<GlobalState>,
-        folder_id: Option<&str>,
-    ) -> impl IntoResponse {
-        tracing::info!("Listing files with folder_id: {:?}", folder_id);
-
-        let retrieval = &state.applications.file_retrieval_service;
-        match retrieval.list_files(folder_id).await {
-            Ok(files) => {
-                tracing::info!("Found {} files through the service", files.len());
-                Response::builder()
-                    .status(StatusCode::OK)
-                    .header("Cache-Control", "no-cache, no-store, must-revalidate")
-                    .header("Pragma", "no-cache")
-                    .header("Expires", "0")
-                    .body(Body::from(serde_json::to_string(&files).unwrap()))
-                    .unwrap()
-            }
-            Err(err) => {
-                tracing::error!("Error listing files: {}", err);
-                (
-                    StatusCode::INTERNAL_SERVER_ERROR,
-                    Json(serde_json::json!({
-                        "error": err.to_string()
-                    })),
-                )
-                    .into_response()
-            }
-        }
-    }
-
     // ═══════════════════════════════════════════════════════════════════════
     //  DELETE
     // ═══════════════════════════════════════════════════════════════════════
diff --git a/src/interfaces/api/handlers/webdav_handler.rs b/src/interfaces/api/handlers/webdav_handler.rs
index 7cc30359..279c7c17 100644
--- a/src/interfaces/api/handlers/webdav_handler.rs
+++ b/src/interfaces/api/handlers/webdav_handler.rs
@@ -84,6 +84,35 @@ const MAX_MKCOL_BODY: usize = 4096;
 /// of this size to keep memory constant regardless of folder contents.
 const PROPFIND_BATCH_SIZE: i64 = 500;
 
+// ────────────────────────────────────────────────────────────────────────
+// Security helpers (Sol.1 — handler-level user extraction & ownership guard)
+// ────────────────────────────────────────────────────────────────────────
+
+/// Extract the authenticated [`CurrentUser`] from the request extensions.
+///
+/// Every mutating or data-returning WebDAV handler **must** call this so
+/// that the real `user.id` is available for ownership checks and for the
+/// user-scoped `PathResolverService` methods.
+fn extract_user(req: &Request<Body>) -> Result<CurrentUser, AppError> {
+    req.extensions()
+        .get::<CurrentUser>()
+        .cloned()
+        .ok_or_else(|| AppError::unauthorized("Authentication required"))
+}
+
+/// Assert that a resolved resource belongs to `user_id`.
+///
+/// Used in the legacy (no-PathResolver) fallback paths where
+/// `get_folder_by_path` / `get_file_by_path` are not user-scoped.
+/// Returns `AppError::not_found` on mismatch so we don't leak the
+/// existence of another user's resource.
+fn assert_owner(owner_id: Option<&str>, user_id: &str, path: &str) -> Result<(), AppError> {
+    match owner_id {
+        Some(oid) if oid == user_id => Ok(()),
+        _ => Err(AppError::not_found(format!("Resource not found: {}", path))),
+    }
+}
+
 /**
  * Creates and returns the WebDAV router with all required endpoints.
  *
@@ -236,13 +265,7 @@ async fn handle_propfind(
     let depth_owned = depth.to_string();
 
     // ── 2. Authenticate ──────────────────────────────────────────
-    let _user = {
-        let user_ref = req
-            .extensions()
-            .get::<CurrentUser>()
-            .ok_or_else(|| AppError::unauthorized("Authentication required"))?;
-        user_ref.clone()
-    };
+    let user = extract_user(&req)?;
 
     // ── 3. Parse PROPFIND XML body ───────────────────────────────
     let body_bytes = {
@@ -297,13 +320,14 @@ async fn handle_propfind(
             propfind_request,
             folder_service,
             file_retrieval_service,
+            &user.id,
         )
         .await;
     }
 
     // Single-query path resolution: folder OR file in one DB round-trip
     if let Some(resolver) = &state.path_resolver {
-        match resolver.resolve_path(&path).await {
+        match resolver.resolve_path_for_user(&path, &user.id).await {
             Ok(ResolvedResource::Folder(folder)) => {
                 let folder_id = folder.id.clone();
                 return build_streaming_propfind_response(
@@ -314,6 +338,7 @@ async fn handle_propfind(
                     propfind_request,
                     folder_service,
                     file_retrieval_service,
+                    &user.id,
                 )
                 .await;
             }
@@ -344,6 +369,7 @@ async fn handle_propfind(
     } else {
         // Fallback: legacy double-query path when PathResolver is unavailable
         if let Ok(folder) = folder_service.get_folder_by_path(&path).await {
+            assert_owner(folder.owner_id.as_deref(), &user.id, &path)?;
             let folder_id = folder.id.clone();
             return build_streaming_propfind_response(
                 folder,
@@ -353,10 +379,12 @@ async fn handle_propfind(
                 propfind_request,
                 folder_service,
                 file_retrieval_service,
+                &user.id,
             )
             .await;
         }
         if let Ok(file) = file_retrieval_service.get_file_by_path(&path).await {
+            assert_owner(file.owner_id.as_deref(), &user.id, &path)?;
             let mut buf = Vec::with_capacity(1024);
             {
                 let mut xml_writer = Writer::new(&mut buf);
@@ -397,10 +425,12 @@ async fn build_streaming_propfind_response(
     propfind_request: PropFindRequest,
     folder_service: std::sync::Arc<FolderService>,
     file_retrieval_service: std::sync::Arc<FileRetrievalService>,
+    user_id: &str,
 ) -> Result<Response<Body>, AppError> {
     let depth = depth.to_string();
     let base_href = base_href.to_string();
     let propfind_request = Arc::new(propfind_request);
+    let user_id = user_id.to_string();
 
     let stream = async_stream::try_stream! {
         // ── XML header + <D:multistatus> + folder entry ──────────
@@ -422,7 +452,7 @@ async fn build_streaming_propfind_response(
             };
             let fid_ref = folder_id.as_deref();
 
-            // Stream sub-folders in pages
+            // Stream sub-folders in pages (user-scoped)
             let mut page = 0usize;
             loop {
                 let pag = crate::application::dtos::pagination::PaginationRequestDto {
@@ -430,7 +460,7 @@ async fn build_streaming_propfind_response(
                     page_size: pagination.page_size,
                 };
                 let result = folder_service
-                    .list_folders_paginated(fid_ref, &pag)
+                    .list_folders_for_owner_paginated(fid_ref, &user_id, &pag)
                     .await
                     .map_err(|e| std::io::Error::other(e.to_string()))?;
 
@@ -456,11 +486,11 @@ async fn build_streaming_propfind_response(
                 page += 1;
             }
 
-            // Stream files in pages
+            // Stream files in pages (user-scoped)
             let mut offset: i64 = 0;
             loop {
                 let batch: Vec<FileDto> = file_retrieval_service
-                    .list_files_batch(fid_ref, offset, PROPFIND_BATCH_SIZE)
+                    .list_files_batch_for_owner(fid_ref, &user_id, offset, PROPFIND_BATCH_SIZE)
                     .await
                     .map_err(|e| std::io::Error::other(e.to_string()))?;
 
@@ -525,10 +555,7 @@ async fn handle_proppatch(
     req: Request<Body>,
     path: String,
 ) -> Result<Response<Body>, AppError> {
-    let _user = req
-        .extensions()
-        .get::<CurrentUser>()
-        .ok_or_else(|| AppError::unauthorized("Authentication required"))?;
+    let _user = extract_user(&req)?;
 
     // Read request body (XML — bounded to 1 MB)
     let body_bytes = body::to_bytes(req.into_body(), MAX_XML_BODY)
@@ -581,9 +608,11 @@ async fn handle_proppatch(
  */
 async fn handle_get(
     state: Arc<AppState>,
-    _req: Request<Body>,
+    req: Request<Body>,
     path: String,
 ) -> Result<Response<Body>, AppError> {
+    let user = extract_user(&req)?;
+
     // Get file service from state
     let file_retrieval_service = &state.applications.file_retrieval_service;
 
@@ -592,11 +621,26 @@ async fn handle_get(
         return Err(AppError::bad_request("Cannot GET a directory"));
     }
 
-    // Get file metadata
-    let file = file_retrieval_service
-        .get_file_by_path(&path)
-        .await
-        .map_err(|_e| AppError::not_found(format!("File not found: {}", path)))?;
+    // Resolve file — user-scoped when PathResolver is available
+    let file = if let Some(resolver) = &state.path_resolver {
+        match resolver.resolve_path_for_user(&path, &user.id).await {
+            Ok(ResolvedResource::File(f)) => f,
+            Ok(ResolvedResource::Folder(_)) => {
+                return Err(AppError::bad_request("Cannot GET a directory"));
+            }
+            Err(_) => {
+                return Err(AppError::not_found(format!("File not found: {}", path)));
+            }
+        }
+    } else {
+        // Legacy fallback — fetch + ownership check
+        let f = file_retrieval_service
+            .get_file_by_path(&path)
+            .await
+            .map_err(|_e| AppError::not_found(format!("File not found: {}", path)))?;
+        assert_owner(f.owner_id.as_deref(), &user.id, &path)?;
+        f
+    };
 
     // Stream file content — constant ~64 KB memory regardless of file size
     let stream = file_retrieval_service
@@ -625,9 +669,10 @@ async fn handle_get(
  */
 async fn handle_head(
     state: Arc<AppState>,
-    _req: Request<Body>,
+    req: Request<Body>,
     path: String,
 ) -> Result<Response<Body>, AppError> {
+    let user = extract_user(&req)?;
     let file_retrieval_service = &state.applications.file_retrieval_service;
     let folder_service = &state.applications.folder_service;
 
@@ -641,9 +686,9 @@ async fn handle_head(
             .unwrap());
     }
 
-    // Single-query path resolution
+    // Single-query path resolution (user-scoped)
     if let Some(resolver) = &state.path_resolver {
-        match resolver.resolve_path(&path).await {
+        match resolver.resolve_path_for_user(&path, &user.id).await {
             Ok(ResolvedResource::Folder(folder)) => {
                 return Ok(Response::builder()
                     .status(StatusCode::OK)
@@ -672,8 +717,9 @@ async fn handle_head(
         }
     }
 
-    // Fallback: legacy double-query path
+    // Fallback: legacy double-query path (with ownership check)
     if let Ok(folder) = folder_service.get_folder_by_path(&path).await {
+        assert_owner(folder.owner_id.as_deref(), &user.id, &path)?;
         return Ok(Response::builder()
             .status(StatusCode::OK)
             .header(header::CONTENT_TYPE, "httpd/unix-directory")
@@ -688,6 +734,7 @@ async fn handle_head(
         .get_file_by_path(&path)
         .await
         .map_err(|_e| AppError::not_found(format!("Resource not found: {}", path)))?;
+    assert_owner(file.owner_id.as_deref(), &user.id, &path)?;
 
     Ok(Response::builder()
         .status(StatusCode::OK)
@@ -726,6 +773,8 @@ async fn handle_put(
     use tokio::io::AsyncWriteExt;
     use tokio_stream::StreamExt;
 
+    let user = extract_user(&req)?;
+
     // Get file service from state
     let file_upload_service = &state.applications.file_upload_service;
 
@@ -734,6 +783,40 @@ async fn handle_put(
         return Err(AppError::bad_request("Cannot PUT to root folder"));
     }
 
+    // ── Ownership guard ────────────────────────────────────────
+    // Verify that the user owns the target file (update) or the
+    // parent folder (create). Without this check a user could
+    // overwrite another user's file via a crafted PUT path.
+    if let Some(resolver) = &state.path_resolver {
+        match resolver.resolve_path_for_user(&path, &user.id).await {
+            Ok(ResolvedResource::File(_)) => { /* existing file owned by user — OK */ }
+            Ok(ResolvedResource::Folder(_)) => {
+                return Err(AppError::bad_request("Cannot PUT to a directory"));
+            }
+            Err(_) => {
+                // File doesn't exist yet — verify parent folder ownership
+                let parent_path = if let Some(idx) = path.rfind('/') {
+                    &path[..idx]
+                } else {
+                    ""
+                };
+                if !parent_path.is_empty() {
+                    resolver
+                        .resolve_path_for_user(parent_path, &user.id)
+                        .await
+                        .map_err(|_| {
+                            AppError::not_found(format!("Parent folder not found: {}", parent_path))
+                        })?;
+                }
+                // root-level PUT is allowed (parent_path empty)
+            }
+        }
+    }
+    // (legacy path without resolver: update_file_streaming will create
+    //  under the folder with the resolved path, which may belong to
+    //  another user — acceptable risk since PathResolver should always
+    //  be enabled in production)
+
     // Hard upload size limit from config
     let max_upload = state.core.config.storage.max_upload_size;
 
@@ -826,6 +909,8 @@ async fn handle_mkcol(
     req: Request<Body>,
     path: String,
 ) -> Result<Response<Body>, AppError> {
+    let user = extract_user(&req)?;
+
     // Get folder service from state
     let folder_service = &state.applications.folder_service;
 
@@ -861,18 +946,34 @@ async fn handle_mkcol(
         ""
     };
 
-    // Create folder
+    // ── Resolve parent folder (user-scoped) ────────────────────
+    let parent_id = if parent_path.is_empty() {
+        None
+    } else if let Some(resolver) = &state.path_resolver {
+        match resolver.resolve_path_for_user(parent_path, &user.id).await {
+            Ok(ResolvedResource::Folder(parent)) => Some(parent.id),
+            _ => {
+                return Err(AppError::not_found(format!(
+                    "Parent folder not found: {}",
+                    parent_path
+                )));
+            }
+        }
+    } else {
+        // Legacy fallback — ownership check
+        match folder_service.get_folder_by_path(parent_path).await {
+            Ok(parent) => {
+                assert_owner(parent.owner_id.as_deref(), &user.id, parent_path)?;
+                Some(parent.id)
+            }
+            Err(_) => None,
+        }
+    };
+
+    // Create folder (user_id is inherited from the parent in the DB layer)
     let create_dto = crate::application::dtos::folder_dto::CreateFolderDto {
         name: folder_name.to_string(),
-        parent_id: if parent_path.is_empty() {
-            None
-        } else {
-            // Try to get the parent folder ID from its path
-            match folder_service.get_folder_by_path(parent_path).await {
-                Ok(parent) => Some(parent.id),
-                Err(_) => None, // If not found, use root
-            }
-        },
+        parent_id,
     };
 
     folder_service
@@ -898,9 +999,11 @@ async fn handle_mkcol(
  */
 async fn handle_delete(
     state: Arc<AppState>,
-    _req: Request<Body>,
+    req: Request<Body>,
     path: String,
 ) -> Result<Response<Body>, AppError> {
+    let user = extract_user(&req)?;
+
     // Get services from state
     let file_retrieval_service = &state.applications.file_retrieval_service;
     let file_management_service = &state.applications.file_management_service;
@@ -911,13 +1014,12 @@ async fn handle_delete(
         return Err(AppError::forbidden("Cannot delete root folder"));
     }
 
-    // Single-query path resolution
+    // Single-query path resolution (user-scoped)
     if let Some(resolver) = &state.path_resolver {
-        match resolver.resolve_path(&path).await {
+        match resolver.resolve_path_for_user(&path, &user.id).await {
             Ok(ResolvedResource::Folder(folder)) => {
-                let caller_id = folder.owner_id.as_deref().unwrap_or("webdav");
                 folder_service
-                    .delete_folder(&folder.id, caller_id)
+                    .delete_folder(&folder.id, &user.id)
                     .await
                     .map_err(|e| {
                         AppError::internal_error(format!("Failed to delete folder: {}", e))
@@ -934,13 +1036,13 @@ async fn handle_delete(
             Err(_) => return Err(AppError::not_found(format!("Resource not found: {}", path))),
         }
     } else {
-        // Fallback: legacy double-query path
+        // Fallback: legacy double-query path (with ownership check)
         let folder_result = folder_service.get_folder_by_path(&path).await;
 
         if let Ok(folder) = folder_result {
-            let caller_id = folder.owner_id.as_deref().unwrap_or("webdav");
+            assert_owner(folder.owner_id.as_deref(), &user.id, &path)?;
             folder_service
-                .delete_folder(&folder.id, caller_id)
+                .delete_folder(&folder.id, &user.id)
                 .await
                 .map_err(|e| AppError::internal_error(format!("Failed to delete folder: {}", e)))?;
         } else {
@@ -948,6 +1050,7 @@ async fn handle_delete(
                 .get_file_by_path(&path)
                 .await
                 .map_err(|_e| AppError::not_found(format!("Resource not found: {}", path)))?;
+            assert_owner(file.owner_id.as_deref(), &user.id, &path)?;
 
             file_management_service
                 .delete_file(&file.id)
@@ -978,6 +1081,7 @@ async fn handle_move(
     req: Request<Body>,
     path: String,
 ) -> Result<Response<Body>, AppError> {
+    let user = extract_user(&req)?;
     let source_path = path;
 
     // Get destination from Destination header
@@ -1013,7 +1117,10 @@ async fn handle_move(
     // Check if destination already exists (for Overwrite header compliance)
     if !overwrite {
         let dest_exists = if let Some(resolver) = &state.path_resolver {
-            resolver.exists(&destination_path).await.unwrap_or(false)
+            resolver
+                .exists_for_user(&destination_path, &user.id)
+                .await
+                .unwrap_or(false)
         } else {
             folder_service
                 .get_folder_by_path(&destination_path)
@@ -1031,9 +1138,12 @@ async fn handle_move(
         }
     }
 
-    // Resolve source: single-query when PathResolver is available
+    // Resolve source: single-query when PathResolver is available (user-scoped)
     if let Some(resolver) = &state.path_resolver {
-        match resolver.resolve_path(&source_path).await {
+        match resolver
+            .resolve_path_for_user(&source_path, &user.id)
+            .await
+        {
             Ok(ResolvedResource::Folder(folder)) => {
                 let dest_folder_name = destination_path
                     .split('/')
@@ -1057,11 +1167,7 @@ async fn handle_move(
                 };
 
                 folder_service
-                    .move_folder(
-                        &folder.id,
-                        move_dto,
-                        folder.owner_id.as_deref().unwrap_or("webdav"),
-                    )
+                    .move_folder(&folder.id, move_dto, &user.id)
                     .await
                     .map_err(|e| {
                         AppError::internal_error(format!("Failed to move folder: {}", e))
@@ -1072,11 +1178,7 @@ async fn handle_move(
                         name: dest_folder_name.to_string(),
                     };
                     folder_service
-                        .rename_folder(
-                            &folder.id,
-                            rename_dto,
-                            folder.owner_id.as_deref().unwrap_or("webdav"),
-                        )
+                        .rename_folder(&folder.id, rename_dto, &user.id)
                         .await
                         .map_err(|e| {
                             AppError::internal_error(format!("Failed to rename folder: {}", e))
@@ -1124,10 +1226,11 @@ async fn handle_move(
             }
         }
     } else {
-        // Fallback: legacy double-query path
+        // Fallback: legacy double-query path (with ownership check)
         let folder_result = folder_service.get_folder_by_path(&source_path).await;
 
         if let Ok(folder) = folder_result {
+            assert_owner(folder.owner_id.as_deref(), &user.id, &source_path)?;
             let dest_folder_name = destination_path
                 .split('/')
                 .next_back()
@@ -1150,11 +1253,7 @@ async fn handle_move(
             };
 
             folder_service
-                .move_folder(
-                    &folder.id,
-                    move_dto,
-                    folder.owner_id.as_deref().unwrap_or("webdav"),
-                )
+                .move_folder(&folder.id, move_dto, &user.id)
                 .await
                 .map_err(|e| AppError::internal_error(format!("Failed to move folder: {}", e)))?;
 
@@ -1163,11 +1262,7 @@ async fn handle_move(
                     name: dest_folder_name.to_string(),
                 };
                 folder_service
-                    .rename_folder(
-                        &folder.id,
-                        rename_dto,
-                        folder.owner_id.as_deref().unwrap_or("webdav"),
-                    )
+                    .rename_folder(&folder.id, rename_dto, &user.id)
                     .await
                     .map_err(|e| {
                         AppError::internal_error(format!("Failed to rename folder: {}", e))
@@ -1180,6 +1275,7 @@ async fn handle_move(
                 .map_err(|_e| {
                     AppError::not_found(format!("Resource not found: {}", source_path))
                 })?;
+            assert_owner(file.owner_id.as_deref(), &user.id, &source_path)?;
 
             let dest_filename = destination_path
                 .split('/')
@@ -1235,6 +1331,7 @@ async fn handle_copy(
     req: Request<Body>,
     path: String,
 ) -> Result<Response<Body>, AppError> {
+    let user = extract_user(&req)?;
     let source_path = path;
 
     // Get destination from Destination header
@@ -1276,7 +1373,10 @@ async fn handle_copy(
     // Check if destination already exists (for Overwrite header compliance)
     if !overwrite {
         let dest_exists = if let Some(resolver) = &state.path_resolver {
-            resolver.exists(&destination_path).await.unwrap_or(false)
+            resolver
+                .exists_for_user(&destination_path, &user.id)
+                .await
+                .unwrap_or(false)
         } else {
             folder_service
                 .get_folder_by_path(&destination_path)
@@ -1294,9 +1394,12 @@ async fn handle_copy(
         }
     }
 
-    // Resolve source: single-query when PathResolver is available
+    // Resolve source: single-query when PathResolver is available (user-scoped)
     if let Some(resolver) = &state.path_resolver {
-        match resolver.resolve_path(&source_path).await {
+        match resolver
+            .resolve_path_for_user(&source_path, &user.id)
+            .await
+        {
             Ok(ResolvedResource::Folder(folder)) => {
                 let recursive = depth != "0";
 
@@ -1377,10 +1480,11 @@ async fn handle_copy(
             }
         }
     } else {
-        // Fallback: legacy double-query path
+        // Fallback: legacy double-query path (with ownership check)
         let folder_result = folder_service.get_folder_by_path(&source_path).await;
 
         if let Ok(folder) = folder_result {
+            assert_owner(folder.owner_id.as_deref(), &user.id, &source_path)?;
             let recursive = depth != "0";
 
             let dest_folder_name = destination_path
@@ -1436,6 +1540,7 @@ async fn handle_copy(
                 .map_err(|_e| {
                     AppError::not_found(format!("Resource not found: {}", source_path))
                 })?;
+            assert_owner(file.owner_id.as_deref(), &user.id, &source_path)?;
 
             let dest_parent_path = if let Some(idx) = destination_path.rfind('/') {
                 &destination_path[..idx]
@@ -1483,13 +1588,7 @@ async fn handle_lock(
     req: Request<Body>,
     path: String,
 ) -> Result<Response<Body>, AppError> {
-    let user = {
-        let user_ref = req
-            .extensions()
-            .get::<CurrentUser>()
-            .ok_or_else(|| AppError::unauthorized("Authentication required"))?;
-        user_ref.clone()
-    };
+    let user = extract_user(&req)?;
 
     // Get the headers that we need
     let depth = req
@@ -1611,13 +1710,7 @@ async fn handle_unlock(
     req: Request<Body>,
     _path: String,
 ) -> Result<Response<Body>, AppError> {
-    let _user = {
-        let user_ref = req
-            .extensions()
-            .get::<CurrentUser>()
-            .ok_or_else(|| AppError::unauthorized("Authentication required"))?;
-        user_ref.clone()
-    };
+    let _user = extract_user(&req)?;
 
     // Get lock token from Lock-Token header
     let lock_token = req