Medium 5.1Published Mar 19, 2026

CVE-2026-27570Discourse Vulnerable to Stored XSS via Shared AI Conversation Onebox

Updated under an hour ago (Oct 28, 2026, 1:50 AM ET)

Does this affect you?

It affects discourse. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

Do this next

Start free and add your stack

Free account, 1 product

Every CVE for discourse

Exploited in the last 30 days

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: 5.1 MEDIUM (v4.0, CNA)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
Weakness (CWE): CWE-79
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Mar 24, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

discourse discourse discourse:discourse (from the name)	from 2026.1.0-latest, < 2026.1.2; from 2026.2.0-latest, < 2026.2.1; = 2026.3.0-latest	CNA record
discourse discourse discourse:discourse	from 2026.1.0 before 2026.1.2; from 2026.2.0 before 2026.2.1; 2026.3.0	NVD

References

References

https://github.com/discourse/discourse/security/advisories/GHSA-hfxw-89hw-vwmv	x-refsource-confirm, vendor-advisory
https://github.com/discourse/discourse/commit/43a5a60b595f0120e6adfc131f2408508fe341f1	x-refsource-misc, patch
https://github.com/discourse/discourse/commit/c14f8f52b7999328bd9f8665f2ecfa24dadc4bf1	x-refsource-misc, patch
https://github.com/discourse/discourse/commit/f2aafa5c7467c94fcd4ebd36785a98e77ca088cc	x-refsource-misc, patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.