CVE-2026-27570mediumCWE-79

Discourse Vulnerable to Stored XSS via Shared AI Conversation Onebox

13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 5.1epss 0.3%

exploitation probability

0.3%top 73% of all CVEs

observed exploitation

nono source reports it

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Affected products

discourse · discourse

References

https://github.com/discourse/discourse/commit/43a5a60b595f0120e6adfc131f2408508fe341f1 https://github.com/discourse/discourse/commit/c14f8f52b7999328bd9f8665f2ecfa24dadc4bf1 https://github.com/discourse/discourse/commit/f2aafa5c7467c94fcd4ebd36785a98e77ca088cc https://github.com/discourse/discourse/security/advisories/GHSA-hfxw-89hw-vwmv