Invoking the Iframe

Add JavaScript to invoke the iframe form POST. Place the JavaScript after the closing
</body>
 tag as shown in the example below. The JavaScript invokes the iframe form POST automatically when the window loads. While you can submit the form at a different time, you must submit the form before requesting the validation service.
<script>
window.onload = function() {   
    var stepUpForm = document.querySelector('#step-up-form');
    if(stepUpForm) // Step-Up form exists
    stepUpForm.submit();
}
</script>