Security fix: The additional_js and additional_js_file_iframe attribute are now only allowed to be used if you have the permission "unfiltered_html", that you need in WordPress to use iframes. If you do not have this permission, during save the attributes are removed and an error message is shown.
Fix: Show iframe as layer was not working properly in Firefox. The link was opening in a new tab. Using a different way to hide the iframe solves the problem.
