CVE-2026-54011

Open WebUI: Stored XSS in Mermaid Markdown Preview

State: Published
Severity: 8.7 High
Published: Jun 23, 2026
Updated: Jun 23, 2026
Reserved: Jun 11, 2026

Description

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.

Scores

CVSS	Score	Vector	Source
3.1	8.7 High	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N	GitHub_M

Weaknesses

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Affected Products

Product	Versions
open-webuiopen-webui	< 0.9.6Affected

References

https://github.com/open-webui/open-webui/security/advisories/GHSA-v8qj-hxv7-mgvv

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