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.