Newsletter < 9.3.8 - Unauthenticated Subscriber PII Disclosure and Modification via Predictable Tracking Signature Key

The Newsletter WordPress plugin before 9.3.8 does not generate its email tracking signing key with sufficient entropy and signs its tracking links with an unkeyed hash, allowing an unauthenticated attacker who recovers that key offline to forge tracking links, obtain any subscriber's session token, and read and modify that subscriber's stored personal data.