Simple User Registration <= 6.9 - Subscriber+ Arbitrary Email Sending via wpr_send_email_to_user

The MemberHero WordPress plugin through 6.9 does not perform any capability or nonce check on one of its AJAX actions, allowing any authenticated user, such as a subscriber, to make the site send arbitrary HTML emails to arbitrary recipients from its own mail system, which can be abused to relay phishing carrying the site's identity and domain reputation.