CVE-2026-27166 MEDIUM

CVE-2026-27166: Discourse vulnerable to HTML injection via prohibited iframe URLs

Vendor Discourse
Product discourse
Weakness CWE-80 · XSS · basic
Published March 19, 2026
Last update March 21, 2026
View on NVD All CVEs

CVSS base score

4.1/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction Required
Confidentiality None
Integrity Low

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N

What the vulnerability does

01Description

Discourse is an open source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2, insufficient cleanup in the default Codepen allowed iframes value allows an attacker to trick a user into changing the URL of the main page. This issue has been fixed in versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2. To workaround this issue, remove Codepen from the list of allowed iframes.

Key dates

02Disclosure timeline

March 19, 2026 CVE published
March 21, 2026 Record updated