Medplum < 5.1.14 SSRF via FHIR Subscription Endpoint

Medplum before 5.1.14 contains a server-side request forgery vulnerability in the subscription worker that allows authenticated users to perform unauthorized internal network requests by creating FHIR Subscription resources with arbitrary endpoint URLs. Attackers can point subscription endpoints at internal addresses such as cloud instance metadata services, internal databases, or container orchestration endpoints to exfiltrate IAM credentials and patient health records via the POST body containing full FHIR resource payloads.