HTML Fields Replacing or Removing Code Entered and Breaking

Hi @faou

I hope you are doing well today.

When it comes to iframe and scripts, Forminator by default removes those tags due to security reasons. However, you can use this code as a mu-plugin:

<?php 

if ( ! function_exists( 'wpmudev_forminator_enable_iframe' ) ) {
    function wpmudev_forminator_enable_iframe() {
        $form_exists = has_shortcode( get_the_content(), 'forminator_form' );
        if ( $form_exists ) {
            ?>
            <script type="text/javascript">
            (($, d) => {
                $(d).ready(function() {
                    $("#forminator-module-1609 #html-1").html('<iframe src="URL"width="100%" height="800" frameBorder="0">');
                });
            })(jQuery, document);
            </script>
            <?php
        }
    }
    add_action( 'wp_footer', 'wpmudev_forminator_enable_iframe', 9999 );
}

Please note, that you should update the form ID (1609) and HTML-1 to your html field. Also, replace the URL with the correct one.

Please find more details here about how to add mu-plugin: https://wpmudev.com/docs/using-wordpress/installing-wordpress-plugins/#installing-mu-plugins

As for ampersand issue can you try this updated code:

<?php

add_filter( 'forminator_form_submit_response', 'wpmudev_fix_response_url_redirect', 20, 2 );
add_filter( 'forminator_form_ajax_submit_response', 'wpmudev_fix_response_url_redirect', 20, 2 );
function wpmudev_fix_response_url_redirect( $response, $form_id ) {
	if ( $form_id != 6 ) {
		return $response;
	}

	if ( ! empty( $response['url'] ) ) {
        $response['url'] = urldecode($response['url']);
        $response['url'] = str_replace('#038;', '&', $response['url']);
	}

	return $response;
}

Kind Regards,
Kris