VibeBP <= 1.9.9.8.1 - Authenticated (Subscriber+) Privilege Escalation in set_email_notification_settings()

The VibeBP plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 1.9.9.8.1. This is due to the plugin allowing arbitrary user meta updates through the set_email_notification_settings() function. This makes it possible for authenticated attackers, with Subscriber-level access and above, to grant themselves administrator privileges by updating their own 'wp_capabilities' user meta value.