Home/CVE/Discourse is an open source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2, insufficie
CVE

CVE-2026-27166

Discourse is an open source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2, insufficie

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.

MEDIUM · CVSS 4.1 EPSS 0.00056
Monitor
  • No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence
Sigma rules0 YARA rules0
⬡

Weakness Classification

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

Affected Products & Versions

4
discourse< 2026.3.0
discourse>= 2026.1.0 and < 2026.1.2
discourse>= 2026.2.0 and < 2026.2.1
discourseall versions
▣

Scoring & Timeline

4.1
MEDIUM · CVSS v3.1 · security-advisories@github.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD19 Mar 2026 · 09:17 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
🔗

References & Sources

2
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/discourse/discourse/commit/c4762a4fac2f61f52f325396b11d3aeb955ea925Patch
https://github.com/discourse/discourse/security/advisories/GHSA-h653-cq78-vjj2Vendor Advisory
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