Medium severity · published Mar 19, 2026
CVE-2026-27570
Discourse Vulnerable to Stored XSS via Shared AI Conversation Onebox
6.1
CVSS
0.4%
EPSS
No
On KEV
Description
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 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)0.4% · higher than 30% 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-2026-27570
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-27570
Patch
https://github.com/discourse/discourse/commit/43a5a60b595f0120e6adfc131f2408508fe341f1
Patch
https://github.com/discourse/discourse/commit/c14f8f52b7999328bd9f8665f2ecfa24dadc4bf1
Patch
https://github.com/discourse/discourse/commit/f2aafa5c7467c94fcd4ebd36785a98e77ca088cc
Vendor Advisory
https://github.com/discourse/discourse/security/advisories/GHSA-hfxw-89hw-vwmv
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