SMS Alert <= 3.9.7 - Unauthenticated Authentication Bypass to Account Takeover via 'billing_phone' Parameter

The SMS Alert – SMS & OTP for WooCommerce, Order Notifications & Abandoned Cart Recovery plugin for WordPress is vulnerable to Authentication Bypass leading to Account Takeover in all versions up to, and including, 3.9.7 via the billing_phone parameter. This is due to the processRegistration() function using a phone-unbound $_SESSION['sa_mobile_verified'] boolean flag as the sole gate before issuing an authentication cookie — the flag is set to true after any successful OTP validation without being bound to the specific phone number that was verified. This makes it possible for unauthenticated attackers to complete OTP verification for a phone number they control, then resubmit the registration request with a victim's billing_phone value to have wp_set_auth_cookie() called for the resolved victim account, enabling full authentication as any existing WordPress user whose registered phone number is known or guessable, including administrators.