Cross-site scripting in Discourse - CVE-2021-37633
Published: August 7, 2021 / Updated: July 1, 2026
Vulnerability identifier: #VU136570
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Green
CVE-ID: CVE-2021-37633
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 attacker to execute arbitrary script in a victim's browser.
The vulnerability exists due to cross-site scripting in d-popover and d-html-popover attribute rendering when rendering tooltip content. A remote attacker can supply crafted content to execute arbitrary script in a victim's browser.
This vulnerability only affects sites that have modified or disabled the default Content Security Policy.
How to mitigate CVE-2021-37633
Install security update from vendor's website.