Open WebUI is an extensible, feature-rich, and user-friendly self-hosted AI platform. From 0.10.0 until 0.11.0, src/lib/components/chat/Messages/Markdown/KatexR…

A stored Cross-Site Scripting (XSS) vulnerability exists in Open WebUI versions 0.10.0 through 0.11.0, affecting the KatexRenderer.svelte component. When a crafted math block causes KaTeX to fail with a stack overflow rather than a parse error, the error catch branch inserts the raw math source as unescaped HTML using Svelte's {@html} directive. This allows arbitrary JavaScript execution in the browser of any user who views the malicious chat message, including shared chats and channels. Attackers can steal session tokens stored in localStorage, enabling account takeover. Administrator accounts are particularly at risk, as compromise could lead to full platform takeover. The vulnerability is fixed in Open WebUI version 0.11.0. A GitHub security advisory and corresponding pull request detail the remediation.