XSS in Discourse
CVE-2026-27570
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.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (25.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 25th percentile — 25.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: -0.000
Affected products
- Discourse — versions = 2026.3.0-latest, >= 2026.2.0-latest, < 2026.2.1, >= 2026.1.0-latest, < 2026.1.2
Weakness classification (CWE)
References
- github.com/discourse/discourse/security/advisories/GHSA-hfxw-89hw-vwmv (Vendor Advisory)
- github.com/discourse/discourse/commit/43a5a60b595f0120e6adfc131f2408508fe341f1 (Patch)
- github.com/discourse/discourse/commit/c14f8f52b7999328bd9f8665f2ecfa24dadc4bf1 (Patch)
- github.com/discourse/discourse/commit/f2aafa5c7467c94fcd4ebd36785a98e77ca088cc (Patch)
Frequently asked questions
- What is CVE-2026-27570?
- CVE-2026-27570 is a medium-severity vulnerability in Discourse, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-03-19.
- How severe is CVE-2026-27570?
- Medium severity. CVSS v3 base score is 6.1 out of 10.