WordPress User Extra Fields <= 16.6 - Missing Authorization to Authenticated (Subscriber+) Privilege Escalation

The WordPress User Extra Fields plugin for WordPress is vulnerable to privilege escalation due to a missing capability check on the ajax_save_fields() function in all versions up to, and including, 16.6. This makes it possible for authenticated attackers, with subscriber-level access and above, to add custom fields that can be updated and then use the check_and_overwrite_wp_or_woocommerce_fields function to update the wp_capabilities field to have administrator privileges.