---
id: CVE-2026-109300
title: >-
  Open WebUI from 0.6.31 before 0.11.4 contains a stored cross-site scripting
  vulnerability in its Markdown renderer, which treats user-authored tool-call
  details blocks as tool output and mounts their embeds attribute in
  script-enabled if…
summary: >-
  Open WebUI from 0.6.31 before 0.11.4 contains a stored cross-site scripting
  vulnerability in its Markdown renderer, which treats user-authored tool-call
  details blocks as tool output and mounts their embeds attribute in
  script-enabled if…
severity: medium
cvss: 4.6
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N'
cwe:
  - CWE-79
published: '2026-10-12'
updated: '2026-10-12'
sourceUpdated: '2026-10-12T17:17:23.700'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-109300'
references:
  - url: >-
      https://github.com/open-webui/open-webui/security/advisories/GHSA-9wj4-mcm3-ppj6
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/open-webui-0.6.31-before-0.11.4-stored-xss-via-tool-call-embeds
    label: disclosure@vulncheck.com
tags:
  - nvd
ingestedAt: '2026-10-12T18:00:08.194Z'
---

## Overview

Open WebUI from 0.6.31 before 0.11.4 contains a stored cross-site scripting vulnerability in its Markdown renderer, which treats user-authored tool-call details blocks as tool output and mounts their embeds attribute in script-enabled iframes. Authenticated users can post crafted channel messages, chat messages, or citation content that runs JavaScript in viewers' browsers, enabling in-app phishing, or session hijacking where iframeSandboxAllowSameOrigin is enabled.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.