html-sanitizer is an allowlist-based HTML cleaner. If using `keep_typographic_whitespace=False` (which is the default), the sanitizer normalizes unicode to the NFKC form at the end. Some unicode characters normalize to chevrons; this allows specially crafted HTML to escape sanitization. The problem has been fixed in 2.4.2.
https://github.com/matthiask/html-sanitizer/security/advisories/GHSA-wvhx-q427-fgh3
https://github.com/matthiask/html-sanitizer/commit/48db42fc5143d0140c32d929c46b802f96913550