Premmerce <= 1.3.20 - Authenticated (Subscriber+) Stored Cross-Site Scripting via 'premmerce_wizard_actions' AJAX Endpoint

The Premmerce plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'premmerce_wizard_actions' AJAX endpoint in all versions up to, and including, 1.3.20. This is due to missing capability checks and insufficient input sanitization and output escaping on the `state` parameter. 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 (the Premmerce Wizard admin page).