PyPI · open-webui
Open WebUI: Same-origin XSS to account takeover via terminal port-preview iframe hardcoding allow-same-origin
Any authenticated user with access to a shared terminal server could get script of their choosing to run in the Open WebUI origin itself. The in-app port preview rendered the content of a previewed port in an iframe whose sandbox always granted allow-same-origin alongside allow-scripts, and that content is served from a path on the application's own origin, so the sandbox provided no isolation at all. Script served on a previewed port could read the victim's session token and take over the account.
TERMINAL_SERVER_CONNECTIONS, empty by default) and reachable by both the attacker and the victim. Deployments with no terminal server configured are not affected.TERMINAL_PROXY_HEADERS unset and no CONTENT_SECURITY_POLICY set, which are the defaults. An operator who had already set a restrictive Content-Security-Policy through either was not exposed, since those headers apply to the proxied response.iframeSandboxAllowSameOrigin user setting is off by default, but the affected branch ignored it entirely.The previewed page runs in the application origin, so it can reach the parent window, read the session token out of localStorage and exfiltrate it, which is full account takeover of the victim. If the victim is an admin, or any user holding workspace.functions, that takeover extends to server-side code execution through Functions. Serving the page costs the attacker nothing beyond the terminal access they already hold, so the only real barrier is getting the victim to open that port. Instances with no terminal server configured were never affected, and neither were personal terminals pointed at an external URL.
Fixed in 0.11.1 by 54d7a2237. The port preview now gates allow-same-origin behind a terminalPreviewAllowSameOrigin user setting that is off by default, so the preview loads at an opaque origin and cannot reach the parent context. Upgrading is sufficient and no configuration change is required. Previews of pages that need same-origin access still work if a user turns that setting on, and doing so re-enables the behaviour described here for that user.
src/lib/components/chat/FileNav/PortPreview.svelte, the preview iframe, reached by clicking a port in the file navigator's port list.Every other iframe in the application had already been moved to an opt-in same-origin setting. The port preview kept a static sandbox string with allow-same-origin baked into it, and it was missed when the equivalent problem was fixed in the file preview for 0.11.0. Because the terminal proxy is mounted under the application's own origin and forwards the upstream response and its content type without adding a Content-Security-Policy of its own unless the operator configured one, and no global CSP is set, the sandbox was the only isolation boundary left, and it was granting precisely the permission that dissolved it.
On a terminal server the victim can also reach, serve an HTML page containing a script that reads window.parent.localStorage.token and sends it to a host the attacker controls. The victim opens the file navigator, switches to the port list and clicks that port. The preview opens, the script executes at the application origin, and the token is exfiltrated.
Reported by @manus-use (researcher zx / Jace).
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Check my repoSources: CISA KEV (public domain), OSV.dev & GitHub Advisory Database (CC-BY-4.0), FIRST EPSS, NVD/CWE (public domain). Served live from the Stateward advisory database.