WPBakery Page Builder Addons by Livemesh <= 3.9.4 - Missing Authorization to Authenticated (Subscriber+) Stored Cross-Site Scripting

Description

The WPBakery Page Builder Addons by Livemesh plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the `lvca_admin_ajax` AJAX action in all versions up to, and including, 3.9.4 due to missing authorization checks and insufficient input sanitization. The AJAX handler verifies a nonce but does not check user capabilities. This makes it possible for authenticated attackers with Subscriber-level access and above to modify plugin settings and inject malicious scripts that execute when administrators access the plugin settings page or when any user visits the frontend.