Vulnerability · Published Jan 28, 2026 · Assigned by GitHub_M

CVE-2025-66488Discourse allows script execution in uploaded HTML/XML files on S3

Medium 4.6

In plain English

A medium-severity security flaw in discourse from discourse. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 10% of all known vulnerabilities).

Severity (CVSS 3.1)4.6Medium

Exploit odds (30 days)0.2%top 90.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Discourse is an open source discussion platform. A vulnerability present in versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0 affects anyone who uses S3 for uploads. While scripts may be executed, they will only be run in the context of the S3/CDN domain, with no site credentials. Versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0 fix the issue. As a workaround, disallow html or xml files for uploads in authorized_extensions. For existing html xml uploads, site owners can consider deleting them.

Affected products (as reported)

Vendor	Product	Versions
discourse	discourse	< 3.5.4>= 2025.11.0-latest, < 2025.11.2>= 2025.12.0-latest, < 2025.12.1>= 2026.1.0-latest, < 2026.1.0

Weakness: CWE-116 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:L

References

https://github.com/discourse/discourse/security/advisories/GHSA-68jp-3934-62rx x_refsource_CONFIRM