CVE-2026-27740

Summary

Discourse is an open-source discussion platform. Versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 have a cross-site scripting vulnerability that arises because the system trusts the raw output from an AI Large Language Model (LLM) and renders it using htmlSafe in the Review Queue interface without adequate sanitization. A malicious attacker can use valid Prompt Injection techniques to force the AI to return a malicious payload (e.g., tags). When a Staff member (Admin/Moderator) views the flagged post in the Review Queue, the payload executes. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. As a workaround, temporarily disable AI triage automation scripts.

Impact & exploitability

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected products we track (1)

Recommendation

Apply the vendor fix in your normal patch cycle. Open any affected product above for its exact safe version.

Official patch: https://github.com/discourse/discourse/commit/44b84439df7e4424b2e7f216fd8fdd7dacff2227 ↗

Additional information

• NVD record
• https://github.com/discourse/discourse/commit/44b84439df7e4424b2e7f216fd8fdd7dacff2227Patch
• https://github.com/discourse/discourse/commit/8ae7cb2414d6918d7fc45e1fda7ffbb32912a975Patch
• https://github.com/discourse/discourse/commit/ed70949f2c047196f33cfa94f2819df29c5d1e5fPatch
• https://github.com/discourse/discourse/security/advisories/GHSA-95hc-42c6-wvvrAdvisory