CVE-2026-45386

### Summary `Pin/Unpin` is a write operation (modifies the message's `is_pinned `, `pinned_by`, `pinned_at` fields), but in standard channels it only checks `read` permission, allowing users with read-only access to pin/unpin any message. ### Details https://github.com/open-webui/open-webui/blob/9bd84258d09eefe7bf975878fb0e31a5dadfe0f8/backend/open_webui/routers/channels.py#L1218 ``` @router.post('/{id}/messages/{message_id}/pin', response_model=Optional[MessageUserResponse]) async def pin_channel_message( request: Request, id: str, message_id: str, form_data: PinMessageForm, user=Depends(get_verified_user), db: Session = Depends(get_session), ): check_channels_access(request) channel = Channels.get_channel_by_id(id, db=db) if not channel: raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=ERROR_MESSAGES.NOT_FOUND) if channel.type in ['group', 'dm']: if not Channels.is_user_channel_member(channel.id, user.id, db=db): raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail=ERROR_MESSAGES.DEFAULT()) else: if user.role != 'admin' and not channel_has_access(user.id, channel, permission='read', db=db): raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail=ERROR_MESSAGES.DEFAULT()) ``` The `channel_has_access` function https://github.com/open-webui/open-webui/blob/9bd84258d09eefe7bf975878fb0e31a5dadfe0f8/backend/open_webui/routers/channels.py#L75 checks user permissions against the `AccessGrants` table: ``` def channel_has_access( user_id: str, channel: ChannelModel, permission: str = 'read', # 'read' or 'write' strict: bool = True, db: Optional[Session] = None, ) -> bool: if AccessGrants.has_access( user_id=user_id, resource_type='channel', resource_id=channel.id, permission=permission, db=db, ): return True # ... ``` The `AccessGrant` table distinguishes bet