Improper authentication

The Premium Packages – Sell Digital Products Securely plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 7.0.4 via the `wpdmppdl` parameter. This is due to the `download()` function — hooked to the unauthenticated WordPress `wp` action — decoding the attacker-controlled `wpdmppdl` parameter using only `base64_decode()` and `json_decode()` with no HMAC, cryptographic signature, or nonce verification, and then issuing WordPress authentication cookies after a domain check that is trivially bypassed because both sides of the comparison are attacker-supplied values. This makes it possible for unauthenticated attackers to authenticate as any non-administrator WordPress user, including subscribers, customers, contributors, authors, editors, and shop managers, who owns an order, gaining full session-level access to that account.