ohader

<?php
// in my_extension/Classes/MyDefaultBuilder.php
namespace OliverHader\MyExtension;

class MyDefaultBuilder extends \TYPO3\CMS\Core\Html\DefaultSanitizerBuilder
{
    protected function createBehavior(): \TYPO3\HtmlSanitizer\Behavior
    {
        // overrides TYPO3's default builder
        // allows `iframe` tag with attrs `src` and `sandbox`