CVE-2026-91122 Details
Description
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the video placeholder component allowed crafted HTML to cause an attribute breakout and inject an attacker-controlled event handler. An authenticated user with default trust-level posting privileges could store the crafted placeholder in a post. When another user opened the post and clicked the video play overlay, the handler could execute arbitrary JavaScript in the viewer's session. Default Content Security Policy settings block inline event handlers, but instances with CSP disabled or relaxed could allow the script to read page content and make authenticated requests as the viewer. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
A stored cross-site scripting vulnerability has been identified in the Discourse video placeholder component, affecting versions prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0. The issue arises because the component's HTML sanitization process does not properly handle double quotes, allowing an authenticated user with default posting privileges to inject a malicious event handler. When another user interacts with the video overlay, the injected JavaScript executes in their session. This vulnerability is particularly concerning for Discourse instances with a relaxed or disabled Content Security Policy, as it could enable the script to access page content and make authenticated requests on behalf of the user.
Users can update to Discourse versions 2026.1.8, 2026.6.3, 2026.7.2, or 2026.8.0 to address this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 24, 2026CISA-ADP
Assessed Sep 24, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-79 | Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Discourse | >= 2026.1.0-latest (semver) >= 2026.6.0-latest (semver) >= 2026.7.0-latest (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 24, 2026 | CVE Modified | CISA-ADP |
| Sep 24, 2026 | New CVE Received | [email protected] |