Untitled

<!DOCTYPE html>
<body>
  parent<br>
  <iframe src="./sca-iframe.html" width="100" height="100" ></iframe>
</body>
<script>
  debugger
  function on3DSComplete() {
    debugger
    console.log("Event received!!!!")
  }
  window.addEventListener('3DS-authentication-complete', on3DSComplete, false);
</script>
</html>

<!DOCTYPE html>
<body>
  iframe
  <script>
    debugger
    window.top.postMessage('3DS-authentication-complete');
    console.log("postMessage('3DS-authentication-complete')")
  </script>
</body>
</html>