CVE-2026-27166CWE-80

Discourse vulnerable to HTML injection via prohibited iframe URLs

Medium · published March 19, 2026

CVSS v3.1
4.1
EPSS
0%
Percentile
18.3
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
4.1 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00271 · 18.3th percentile
Weakness
CWE-80 · Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)
Published
2026-03-19T20:29Z
EPSS history
Timeline
  • 19 MAR 20:29Z
    Discourse vulnerable to HTML injection via prohibited iframe URLs
    cvelistv5