The Groundhogg — CRM, Newsletters, and Marketing Automation plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 4.5.2 via the GET /wp-json/gh/v4/contacts/<id> REST endpoint. The endpoint's permission callback checks only the role-level viewcontacts capability and readsingle() returns the full contact record by sequential integer ID without the object-level viewcontact ownership check applied elsewhere in the codebase. This makes it possible for authenticated attackers holding viewcontacts but not viewotherscontacts — notably Groundhogg's built-in Sales Rep role, designed to see only its own contacts — to read any contact record on the site, including PII, contact meta, owner IDs, the admin edit URL, and (for contacts linked to a WordPress user) that user's full capability set.