CVE-2026-91159 Discourse - Stored XSS

Discourse < 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9 contains a stored XSS caused by trusted processing of attacker-controlled HTML fragments with allowlisted iframes in oEmbed, letting users with posting permission inject misleading UI, exploit requires posting account and control of allowlisted iframe source.

CVSS base score 7.7 /10
High
CISA KEV
Not listed
Public exploit
Proof of concept available
Authentication
Required
View the NVD record ↗

Details

Type
Stored XSS
Impact
Stored XSS
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
Published
14 October 2026
Updated
15 October 2026
Weakness
CWE-79

Vendor fix

Update to versions 2026.9.0, 2026.8.1, 2026.7.3, or 2026.1.9.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

← All CVEs