Welcart e-Commerce <= 2.12.5 - Account Takeover via Insecure Direct Object Reference to Unauthenticated User Input via 'member[ID]' Parameter

The Welcart e-Commerce plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 2.12.5 via the 'member[ID]' parameter due to missing validation on a user controlled key. This makes it possible for unauthenticated attackers to overwrite any existing Welcart shop-member account's email address and password by supplying that member's numeric ID, then authenticate as that member to achieve full account takeover. The only authentication barrier is a wp_verify_nonce() check against a nonce printed to every unauthenticated visitor on the auto-published New Enrollment Form, meaning no existing account, no WordPress login, and no non-default configuration is required to exploit this vulnerability.