Open WebUI: A folder write-collaborator can permanently delete the owner's chats by deleting a shared subfolder

Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.10.0 until 0.11.0, the DELETE /api/v1/folders/{id} handler in backend/open_webui/routers/folders.py allowed a user granted write access to a shared chat folder to permanently delete chats and messages belonging to the folder owner. The cascade following the authorization check is bound to the folder owner's id, but the subfolder check accepted any inherited write grant instead of requiring ownership or administrator status. A collaborator can destroy the owner's subtree or force-move chats out of it when delete_contents=false. This issue is fixed in 0.11.0.