OpenEMR before 8.4.0 FHIR Patient Compartment Bypass via Person Endpoint

OpenEMR before 8.4.0 contains an authorization bypass vulnerability in the FHIR GET /fhir/Person/:uuid route that allows patient-portal users to read any staff member's demographics by bypassing compartment enforcement. Attackers holding a patient SMART token with patient/Person.read can harvest staff Person UUIDs from Appointment references to retrieve names, home addresses, phone numbers, and personal emails.