https://vulnerability.circl.lu/rss/recent/all/10 Most recent entries from all 2026-10-03T23:34:10.670530+00:00 Vulnerability-Lookup info@circl.lu python-feedgen Contains only the most 10 recent entries. https://vulnerability.circl.lu/vuln/cve-2026-54011 CVE-2026-54011 — Open WebUI: Stored XSS in Mermaid Markdown Preview 2026-10-03T23:34:10.701231+00:00

Affected: open-webui

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.6,Open WebUI renders Mermaid blocks from Markdown files in the file preview panel and inserts the generated SVG into the DOM using innerHTML. Because Mermaid is configured with securityLevel: 'loose', attacker-controlled Mermaid content can be rendered unsafely in this flow. A working payload was validated through the Markdown preview path, resulting in JavaScript execution in the victim’s browser under the application origin. This vulnerability is fixed in 0.9.6.

 https://vulnerability.circl.lu/vuln/ghsa-v8qj-hxv7-mgvv GHSA-v8qj-hxv7-mgvv — Open WebUI: Stored XSS in Mermaid Markdown Preview 2026-10-03T23:34:10.701365+00:00

Affected: PyPI: open-webui

## Summary

Open WebUI renders Mermaid blocks from Markdown files in the file preview panel and inserts the generated SVG into the DOM using `innerHTML`.

Because Mermaid is configured with `securityLevel: 'loose'`, attacker-controlled Mermaid content can be rendered unsafely in this flow. A working payload was validated through the Markdown preview path, resulting in JavaScript execution in the victim’s browser under the application origin.

This is a confirmed stored XSS vulnerability reachable through normal product functionality.

## Affected Version

- `main` - Reproduced on `v0.8.12`

## Affected Code

Mermaid is initialized in permissive mode:

https://github.com/open-webui/open-webui/blob/9bd84258d09eefe7bf975878fb0e31a5dadfe0f8/src/lib/utils/index.ts#L1698 The file preview path renders Mermaid output and injects the returned SVG into the DOM:

https://github.com/open-webui/open-webui/blob/9bd84258d09eefe7bf975878fb0e31a5dadfe0f8/src/lib/components/chat/FileNav/FilePreview.svelte#L133

## Impact

A successful exploit allows JavaScript execution in the victim’s browser under the Open WebUI origin when a malicious Markdown file is opened in the preview panel.

## PoC

A malicious `.md` file containing the follwowing contents can be used to trigger the bug: ```` ```mermaid flowchart LR A[click me] click A href "javascript:alert(document.domain)" "x" ``` ```` Steps to reproduce: 1- Create a new chat 2- Enable Code Interpreter and browse and upload the file with `.m…