Open WebUI: Any authenticated user can reach internal services and cloud metadata via NAT64-encoded URLs

Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.9.0 until 0.11.0, Open WebUI checked whether a user-supplied URL destination was globally routable by applying ipaddress.is_global to the literal IPv6 address without examining IPv4 addresses embedded in transition encodings. On a deployment with a NAT64 gateway, any verified user could wrap an internal or cloud-metadata IPv4 address in the NAT64 well-known prefix, pass the filter, and receive the internal response body through RAG URL ingestion, URL-to-markdown conversion, or web-search content retrieval. This issue is fixed in 0.11.0.