Open WebUI: Any authenticated user can inject chats into another user's folder via chat completions

Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.10.0 until 0.11.1, POST /api/chat/completions and POST /api/v1/chat/completions in backend/open_webui/main.py copied a client-supplied folder_id into a new chat without applying the folder write-access check used by the dedicated chat routes. An authenticated user who knew a shared folder identifier could inject an attacker-controlled chat into a folder where the user had read-only or no write access, causing the entry to appear to authorized folder readers. This issue is fixed in version 0.11.1.