Cross-site scripting in Discourse - CVE-2026-33395
Published: July 1, 2026
Vulnerability identifier: #VU136134
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-33395
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Civilized Discourse Construction Kit, Inc.
Affected software:
Discourse
Discourse
Detailed vulnerability description
The vulnerability allows a remote user to inject malicious JavaScript code.
The vulnerability exists due to cross-site scripting in the discourse-graphviz plugin when processing DOT graph definitions. A remote user can submit a specially crafted graph definition to inject malicious JavaScript code.
Only instances with CSP disabled are vulnerable. User interaction is required to view the stored content.
How to mitigate CVE-2026-33395
Install security update from vendor's website.