Vulnerability Report: GO-2022-0588

• CVE-2021-42576, GHSA-x95h-979x-cf3j
• Affects: github.com/microcosm-cc/bluemonday
• Published: Aug 15, 2022
• Modified: Dec 14, 2023

The bluemonday HTML sanitizer can leak the contents of a "style" element into HTML output, potentially causing XSS vulnerabilities. The default bluemonday sanitization policies are not vulnerable. Only user-defined policies allowing "select", "style", and "option" elements are affected. Permitting the "style" element in policies is hazardous, because bluemonday does not contain a CSS sanitizer. Newer versions of bluemonday suppress "style" and "script" elements even when allowed by a policy unless the policy explicitly requests unsafe processing.