Yes, you can use SA5’s User Info lib to access a logged in user’s email, name, custom fields and access groups.
On page load, an event is fired with the User object and you can pull the custom user data field you want.
The custom code would something look like this, and go only on the page with your IFRAME ( before head area ). Let’s suppose your IFRAME has an ID of my-iframe and your custom user field is named iframe-link.
<script>
window.sa5 = window.sa5 || [];
window.sa5.push(['userInfoChanged',
(user) => {
if(user.user_data_loaded.custom_fields) {
// Here you apply your custom data URL to your IFRAME src
document.getElementById('my-iframe').src = user.data['iframe-link'];
}
}]);
</script>