CVE-2026-27166 PUBLISHED

Discourse vulnerable to HTML injection via prohibited iframe URLs

Assigner: GitHub_M
Reserved: 18.02.2026 Published: 19.03.2026 Updated: 19.03.2026

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.

Metrics

CVSS 3.1

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

Attack Vector	Network	Scope	Changed
Attack Complexity	Low	Confidentiality Impact	None
Privileges Required	Low	Integrity Impact	Low
User Interaction	Required	Availability Impact	None

CVSS 3.1

Product Status

Vendor	discourse
Product	discourse
Versions	Version < 2026.3.0-latest.1 is affected Version >= 2026.2.0-latest, < 2026.2.1 is affected Version >= 2026.1.0-latest, < 2026.1.2 is affected

References

Problem Types

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