CVE-2026-54007: Open WebUI: Cross-origin postMessage confirmation bypass via action:submit

June 17, 2026 (updated August 13, 2026)

The chat message listener allows non-same-origin input:prompt and action:submit messages, so an external site can set prompt text and trigger submitPrompt() in an authenticated victim session. I validated this with a cross-origin attacker page that auto-posted messages and caused unauthorized POST /api/v1/chats/new and POST /api/chat/completions requests containing attacker-controlled prompts. This enables cross-site forced actions and model/tool execution under victim privileges without consent.

References

Code Behaviors & Features

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