Medium severity · published Mar 19, 2026
CVE-2026-27740
Discourse has Stored XSS in AI Triage Automation
6.1
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 27% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
DI
discourse · discourse
>= 2026.1.0-latest, < 2026.1.2; >= 2026.2.0-latest, < 2026.2.1; = 2026.3.0-latest · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-27740
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-27740
Patch
https://github.com/discourse/discourse/commit/44b84439df7e4424b2e7f216fd8fdd7dacff2227
Patch
https://github.com/discourse/discourse/commit/8ae7cb2414d6918d7fc45e1fda7ffbb32912a975
Patch
https://github.com/discourse/discourse/commit/ed70949f2c047196f33cfa94f2819df29c5d1e5f
Vendor Advisory
https://github.com/discourse/discourse/security/advisories/GHSA-95hc-42c6-wvvr
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