CVE-2026-27740

Name of the Vulnerable Software and Affected Versions Discourse versions prior to 2026.3.0-latest.1 Discourse versions prior to 2026.2.1 Discourse versions prior to 2026.1.2

Description Discourse, an open-source discussion platform, is affected by a cross-site scripting issue. The system improperly trusts and renders output from an AI Large Language Model (LLM) using htmlSafe within the Review Queue interface, lacking sufficient sanitization. An attacker can leverage Prompt Injection techniques to make the AI generate a malicious payload, such as tags. When a staff member (Admin/Moderator) views a flagged post in the Review Queue, this payload is executed.

Recommendations Versions prior to 2026.3.0-latest.1 should be updated. Versions prior to 2026.2.1 should be updated. Versions prior to 2026.1.2 should be updated. As a temporary workaround, disable AI triage automation scripts.