Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.3, the POST /api/v1/notes/{id}/pin endpoint performs a write operation (toggling the is_pinned field) but only checks for read permission. Users with read-only access to a shared note can pin/unpin it, which is a state-modifying action that should require write permission. This vulnerability is fixed in 0.9.3.

Affected: PyPI: open-webui

### Summary

The `POST /api/v1/notes/{id}/pin` endpoint performs a write operation (toggling the `is_pinned` field) but only checks for `read` permission. Users with read-only access to a shared note can pin/unpin it, which is a state-modifying action that should require `write` permission. All other write endpoints (update, delete, access/update) correctly check for `write` permission.

### Details

**Affected code: `backend/open_webui/routers/notes.py` lines 412-444**

```python @router.post('/{id}/pin', response_model=Optional[NoteModel]) async def pin_note_by_id(...): # ... if user.role != 'admin' and ( user.id != note.user_id and not await AccessGrants.has_access( user_id=user.id, resource_type='note', resource_id=note.id, permission='read', # BUG: should be 'write' db=db, ) ): raise HTTPException(...) note = await Notes.toggle_note_pinned_by_id(id, db=db) # write operation ```

**Compare with update endpoint (correct, line 318-327):** ```python async def update_note_by_id(...): # ... and not await AccessGrants.has_access( permission='write', # correctly checks 'write' ) ```

### PoC

**Environment:** Open WebUI v0.9.2, default configuration with notes sharing enabled.

**Setup:** 1. UserA creates a note 2. UserA shares note with UserB with `read` permission via `POST /api/v1/notes/{id}/access/update` with `{"access_grants":…

Affected: PyPI: open-webui

### Summary

The `POST /api/v1/notes/{id}/pin` endpoint performs a write operation (toggling the `is_pinned` field) but only checks for `read` permission. Users with read-only access to a shared note can pin/unpin it, which is a state-modifying action that should require `write` permission. All other write endpoints (update, delete, access/update) correctly check for `write` permission.

### Details

**Affected code: `backend/open_webui/routers/notes.py` lines 412-444**

```python @router.post('/{id}/pin', response_model=Optional[NoteModel]) async def pin_note_by_id(...): # ... if user.role != 'admin' and ( user.id != note.user_id and not await AccessGrants.has_access( user_id=user.id, resource_type='note', resource_id=note.id, permission='read', # BUG: should be 'write' db=db, ) ): raise HTTPException(...) note = await Notes.toggle_note_pinned_by_id(id, db=db) # write operation ```

**Compare with update endpoint (correct, line 318-327):** ```python async def update_note_by_id(...): # ... and not await AccessGrants.has_access( permission='write', # correctly checks 'write' ) ```

### PoC

**Environment:** Open WebUI v0.9.2, default configuration with notes sharing enabled.

**Setup:** 1. UserA creates a note 2. UserA shares note with UserB with `read` permission via `POST /api/v1/notes/{id}/access/update` with `{"access_grants":…