CVE-2026-27166

MEDIUM

Discourse vulnerable to HTML injection via prohibited iframe URLs

Title source: cna
STIX 2.1

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.

References (2)

Core 2

Scores

CVSS v3 4.1
EPSS 0.0019
EPSS Percentile 8.4%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact partial

Details

CWE
CWE-80
Status published
Products (5)
discourse/discourse 2026.3.0
discourse/discourse < 2026.3.0
discourse/discourse < 2026.3.0-latest.1
discourse/discourse >= 2026.1.0-latest, < 2026.1.2
discourse/discourse >= 2026.2.0-latest, < 2026.2.1
Published Mar 19, 2026
Tracked Since Mar 20, 2026