The Ninja Forms - Excel Export plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to, and including, 3.3.6. This is due to the savefilter() AJAX handler storing the raw $POST['filter'] array into a WordPress option via updateoption() without any capability check, nonce verification, or input sanitization, combined with the getfilterrow() method on the admin Excel Export screen concatenating the stored filter values (fieldkey, condition, value) directly into HTML attributes without escattr(). This makes it possible for authenticated attackers, with subscriber-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.