I'm developing a Wordpress plugin (integrated with **WooCommerce**) that fetches HTML Content from an API, and add it to a WP Post as post_content into an iframe, this way:


    kses_remove_filters();
    $newData['description'] = str_replace("\n", "", $newData['description']);
    $newData['description'] = str_replace("\t", "", $newData['description']);
    $post = $this->getPostByAPIId($product->api_id);

    $id = $post->ID ?? get_post($product->woo_id)->ID;
    if (isset($id) && !empty($id)) {
        $this->wpdb->update(
            "{$this->wpdb->prefix}posts",
            [
                'post_content'  => '<iframe class="custom-post" id="custom_product_post_content" src="' . htmlspecialchars('data:text/html,' . stripslashes(rawurlencode($newData['description']))) . '" style="display: block;width:100vw; height:100vh; border:none; margin:0; padding:0; overflow:hidden; z-index:999999; min-height:300px!important;"></iframe>'
            ],
            [
                'ID' => $id
            ]
        );
    }
    kses_init_filters();

Even if I put the **kses_remove_filters()**, when I open wordpress to check the new content, I find out that the *post_content* is empty.

If I try to debug the plugin with xdebug, I find out that post_content is updated, but when I refresh wordpress, the post_content disappear.

A few project specifications before starting:

 1. I can't just embed the API as src
 2. I don't want to fetch content via javascript
 3. I used an **iframe** because I know that wordpress post_content can't embed a full HTML page like this: <code>html > head { title } > body { style and various tags }</code>    
 4. I don't write the HTML personally, I need to embed it via the API

Feel free to ask any question. Thanks in advance.

Edit: Even if I use <code>wp_update_post(['ID' => $id, 'post_content' => '...'])</code> the post_content doesn't get updated and I get empty content.