CVE-2025-66488
Discourse allows script execution in uploaded HTML/XML files on S3
6.1
MEDIUM
CVSS 3.1
EPSS 0.02%
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.
How to fix CVE-2025-66488
To remediate CVE-2025-66488, upgrade the affected package to a fixed version below.
- —upgrade to 3.5.4 or later
Is CVE-2025-66488 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 3.5.4, >= 2025.11.0, < 2025.11.2, >= 2025.12.0, < 2025.12.1, >= 2026.1.0, < 2026.1.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |