CVE-2026-97657: Abandoned Cart Pro for WooCommerce <= 10.8.0 - Unauthenticated Authentication Bypass via Malleable Encryption and Bypassable HMAC via Recovery Link 'validate' Parameter

The Abandoned Cart Pro for WooCommerce plugin for WordPress is vulnerable to Authentication Bypass via Malleable Encryption and Bypassable HMAC in all versions up to, and including, 10.8.0. This is due to the use of MAC-free AES-CTR encryption for cart-recovery link tokens — where the 8-byte CTR nonce is carried inside the ciphertext blob and the encryption key is looked up using the attacker-supplied `user_email` GET parameter — combined with an HMAC nonce check in `wcap_email_track_links()` that is only enforced when the `wcap_nonce` parameter is non-empty, allowing complete bypass by omission, and an insecure direct object reference on the decrypted `abandoned_id` with no ownership verification confirming the cart belongs to the email used for decryption. This makes it possible for unauthenticated attackers who possess a single legitimate cart-recovery link (obtained from their own reminder email) to recover the keystream, forge a ciphertext that decrypts to any victim's cart ID, and trigger a call to `wp_set_auth_cookie()` for the victim user — achieving full account takeover of any user who has ever abandoned a cart, including administrators. The auto-login feature defaults to enabled and is forced on during plugin upgrades, meaning all affected installations are exploitable without any additional configuration.