CVE-2026-54011

Open WebUI: Stored XSS in Mermaid Markdown Preview

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.

Affected

open-webui

CVSS v3.1 NVD

5.4 MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CVSS v3.1 GITHUB

8.7 HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

EPSS

0.34% chance of exploitation in the next 30 days, 26th percentile

Published

2026-06-23

Proof-of-concept exploits (1)

• advisories/GHSA-v8qj-hxv7-mgvv

Security advisories

• open-webui/open-webui/security/advisories/GHSA-v8qj-hxv7-mgvv

References

• CVE Record
• NVD entry