CVE-2026-27740
Discourse has Stored XSS in AI Triage Automation
- State
- Published
- Severity
- 5.1 Medium
- Published
- Mar 19, 2026
- Updated
- Mar 20, 2026
- Reserved
- Feb 23, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 5.1 Medium | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N | GitHub_M |
Weaknesses
- CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Products
| Product | Versions |
|---|---|
discoursediscourse |
|
References
- https://github.com/discourse/discourse/security/advisories/GHSA-95hc-42c6-wvvr
- https://github.com/discourse/discourse/commit/44b84439df7e4424b2e7f216fd8fdd7dacff2227
- https://github.com/discourse/discourse/commit/8ae7cb2414d6918d7fc45e1fda7ffbb32912a975
- https://github.com/discourse/discourse/commit/ed70949f2c047196f33cfa94f2819df29c5d1e5f
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