JetFormBuilder <= 3.3.4.1 - Authenticated (Administrator+) Privilege Escalation

The JetFormBuilder plugin for WordPress is vulnerable to privilege escalation in all versions up to, and including, 3.3.4.1. This is due to improper restriction on user meta fields. This makes it possible for authenticated attackers, with administrator-level and above permissions, to register as super-admins on the sites configured as multi-sites.