Cross-site scripting in Discourse - #VU140004
Published: July 29, 2026
Vulnerability identifier: #VU140004
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Clear
CVE-ID: N/A
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Affected software:
Discourse
Discourse
Detailed vulnerability description
The vulnerability allows a remote user to execute arbitrary script code in a victim's browser.
The vulnerability exists due to improper neutralization of input during web page generation in the rich text editor transcript header rendering when processing chat transcript quote metadata. A remote user can supply a specially crafted username in quote metadata to execute arbitrary script code in a victim's browser.
User interaction is required to view the crafted content in the rich text editor.
Remediation
Install security update from vendor's website.