The WP App Bar plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'app-bar-features' parameter in all versions up to, and including, 1.5. This is due to insufficient input sanitization and output escaping combined with a missing authorization check in the App_Bar_Settings class constructor. This makes it possible for unauthenticated attackers to inject arbitrary web scripts into multiple plugin settings that will execute whenever a user accesses the admin settings page.