CVE-2026-86867

Cinnamon's Kotaemon (all versions up to and including v0.12.0) multi-user chat interface contains multiple vulnerabilities due to incorrect authorization and improper access controls. There are four handler methods in `libs/ktem/ktem/pages/chat/control.py` that load a Conversation record by its ID without comparing the requester's `user_id` to the conversation's owner `Conversation.user`. This allows any authenticated user to perform the following actions:
1. Read other user's chat transcripts, RAG retrieval history, AI-generated plots, and chat suggestions.
2. Permanently delete another user's conversation.
3. Rename another user's conversation.
4. Overwrite another user's conversation's chat suggestion list.