Missing authorization

The Participants Database plugin for WordPress is vulnerable to Sensitive Information Exposure in all versions up to, and including, 2.7.8.3 via the 'id' parameter. This makes it possible for unauthenticated attackers to overwrite arbitrary participant records by numeric ID and redirect the private_id-bearing record-access link to an attacker-controlled email address, granting full read and edit access to the victim's stored personally identifiable information including names, email addresses, phone numbers, and any other fields collected in the participant database. An attacker can harvest a valid nonce with a plain unauthenticated GET request to any page rendering the public signup or record form, then POST action=update with an arbitrary id value to overwrite any record; chaining a subsequent action=retrieve then delivers the private-access link to the attacker-controlled mailbox.