The Funnelforms Free plugin for WordPress is vulnerable to unauthorized modification of data due to a missing capability check on the fnsf_af2_test_mail function in versions up to, and including, 3.4. This makes it possible for authenticated attackers, with subscriber-level permissions and above, to send test emails to an arbitrary email address.
https://plugins.trac.wordpress.org/changeset/2986938/funnelforms-free