CVE-2026-87013: Open WebUI: Any authenticated user can start a non-terminating request via a folder parent cycle

Any authenticated user can move one of their own folders under itself, leaving a loop in their folder tree. The re-parent endpoint performed no check that the new parent was not the folder itself or one of its own subfolders, and the folder tree walks did not track which folders they had already visited. A single request against a folder in a loop therefore never finishes.