XSS via Onebox in Discourse <=2026.2.1
CVE-2026-27570 Published on March 19, 2026
Discourse Vulnerable to Stored XSS via Shared AI Conversation Onebox
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the onebox method in the SharedAiConversation model renders the conversation title directly into HTML without proper sanitization. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. As a workaround, tighten access by changing the `ai_bot_public_sharing_allowed_groups` site setting.
Weakness Type
What is a XSS Vulnerability?
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
CVE-2026-27570 has been classified to as a XSS vulnerability or weakness.
Products Associated with CVE-2026-27570
Want to know whenever a new CVE is published for Discourse? stack.watch will email you.
Affected Versions
discourse:- Version >= 2026.1.0-latest, < 2026.1.2 is affected.
- Version >= 2026.2.0-latest, < 2026.2.1 is affected.
- Version = 2026.3.0-latest is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.