The CSS & JavaScript Toolbox plugin for WordPress is vulnerable to Stored Cross-Site Scripting in all versions up to, and including, 12.0.6 via the Assignment Engine fields. This is due to insufficient input sanitization and output escaping on assignment data fields including Expressions, URLs, and Advanced assignment data. This makes it possible for authenticated attackers, with Administrator-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses the CJT block edit screen in the admin dashboard.