The CMB2 plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'file_list' Field Type in all versions up to, and including, 2.13.0 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This is only exploitable when an integrating plugin or theme registers a file_list field on a publicly accessible front-end form or a user meta box, as CMB2 is a developer library and does not expose these fields by default.