CVE-2026-27166

Discourse vulnerable to HTML injection via prohibited iframe URLs

State: Published
Severity: 4.1 Medium
Published: Mar 19, 2026
Updated: Mar 21, 2026
Reserved: Feb 18, 2026

Description

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.

Scores

CVSS	Score	Vector	Source
3.1	4.1 Medium	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N	GitHub_M

Weaknesses

CWE-80 Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)

Affected Products

Product	Versions
discoursediscourse	< 2026.3.0-latest.1Affected >= 2026.2.0-latest, < 2026.2.1Affected >= 2026.1.0-latest, < 2026.1.2Affected

References

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