The CMB2 plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'cmb43ex1_grp[0][txt] (wysiwyg field inside group — field id controlled by integrator config)' parameter in all versions up to, and including, 2.13.4 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 a site integrator renders the plugin's documented front-end form helper with a wysiwyg field inside a repeatable group on a publicly accessible page.