Cross-site scripting in Discourse - CVE-2026-59830
Published: July 29, 2026
Vulnerability identifier: #VU140000
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: CVE-2026-59830
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 the victim's browser.
The vulnerability exists due to improper neutralization of input during web page generation in post actions on user activity streams when rendering user-controlled display names in an HTML string passed to trustHTML. A remote user can set a crafted actor name to execute arbitrary script code in the victim's browser.
User interaction is required to view the affected activity stream.
How to mitigate CVE-2026-59830
Install security update from vendor's website.