The Co-Authors, Multiple Authors and Guest Authors in an Author Box with PublishPress Authors plugin for WordPress is vulnerable to Insecure Direct Object Reference to Privilege Escalation/Account Takeover in all versions up to, and including, 4.7.1 via the action_edited_author() due to missing validation on the 'authors-user_id' user controlled key. This makes it possible for authenticated attackers, with Author-level access and above, to update arbitrary user accounts email addresses, including administrators, which can then be leveraged to reset that user's account password and gain access.