The CMB2 plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'cmb43ex1grp[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.

The CMB2 plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the '<textareacode field id> (e.g. klcode, klpostcode)' parameter in all versions up to, and including, 2.13.1 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. The front-end save path requires only a CMB2 box nonce, which is emitted to all visitors including unauthenticated guests via a simple GET request, making the attack trivially reachable without any credentials on sites that expose a public CMB2 form writing a textareacode field.

The CMB2 plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'filelist' 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 filelist 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.

The CMB2 WordPress plugin before 2.13.0 does not perform any capability check on one of its AJAX actions, allowing users with a role as low as Subscriber to create arbitrary WordPress options and corrupt existing ones, which can break core site settings and take the site offline. Exploitation requires the site's or another CMB2 WordPress plugin before 2.13.0 to have declared an oEmbed field, as the CMB2 WordPress plugin before 2.13.0 registers none of its own. The stored value is never attacker-controlled, so the issue does not lead to privilege escalation.