AIKIDO-2026-420462

TL;DR

Affected versions of @clerk/shared are vulnerable to stored Cross-site Scripting (XSS) when Clerk auth state is serialized into SSR <script> tags. JSON.stringify leaves <, >, and / unescaped, so a </script> sequence inside user-controllable session claims can break out of the script element and execute arbitrary JavaScript. The fix introduces htmlSafeJson, which escapes those characters (and U+2028/U+2029) to Unicode escapes so the embedded JSON still parses to identical values on the client.