add_filter('content_save_pre','iframe_save_pre');
  
function iframe_save_pre($content){
    global $allowedposttags;
    $allowedposttags['iframe'] = array('class' => array () , 'src'=>array() , 'width'=>array(),
    'height'=>array() , 'frameborder' => array() , 'scrolling'=>array(), 'marginheight'=>array(),
    'marginwidth'=>array());
  
    return $content;
}{"version":"1.0","provider_name":"\u7fbd\u7530\u30b9\u30bf\u30b8\u30aa  HANEDA ENTERTAINMENT STUDIO - Tokyo Japan","provider_url":"https:\/\/haneda-st.com","author_name":"mg.haneda","author_url":"https:\/\/haneda-st.com\/author\/mg-haneda","title":"Concert","type":"rich","width":600,"height":338,"html":"<blockquote class=\"wp-embedded-content\"><a href=\"https:\/\/haneda-st.com\/example\/concert.html\">Concert<\/a><\/blockquote>\n<script type='text\/javascript'>\n<!--\/\/--><![CDATA[\/\/><!--\n\t\t\/*! This file is auto-generated *\/\n\t\t!function(c,d){\"use strict\";var e=!1,n=!1;if(d.querySelector)if(c.addEventListener)e=!0;if(c.wp=c.wp||{},!c.wp.receiveEmbedMessage)if(c.wp.receiveEmbedMessage=function(e){var t=e.data;if(t)if(t.secret||t.message||t.value)if(!\/[^a-zA-Z0-9]\/.test(t.secret)){for(var r,a,i,s=d.querySelectorAll('iframe[data-secret=\"'+t.secret+'\"]'),n=d.querySelectorAll('blockquote[data-secret=\"'+t.secret+'\"]'),o=0;o<n.length;o++)n[o].style.display=\"none\";for(o=0;o<s.length;o++)if(r=s[o],e.source===r.contentWindow){if(r.removeAttribute(\"style\"),\"height\"===t.message){if(1e3<(i=parseInt(t.value,10)))i=1e3;else if(~~i<200)i=200;r.height=i}if(\"link\"===t.message)if(a=d.createElement(\"a\"),i=d.createElement(\"a\"),a.href=r.getAttribute(\"src\"),i.href=t.value,i.host===a.host)if(d.activeElement===r)c.top.location.href=t.value}}},e)c.addEventListener(\"message\",c.wp.receiveEmbedMessage,!1),d.addEventListener(\"DOMContentLoaded\",t,!1),c.addEventListener(\"load\",t,!1);function t(){if(!n){n=!0;for(var e,t,r=-1!==navigator.appVersion.indexOf(\"MSIE 10\"),a=!!navigator.userAgent.match(\/Trident.*rv:11\\.\/),i=d.querySelectorAll(\"iframe.wp-embedded-content\"),s=0;s<i.length;s++){if(!(e=i[s]).getAttribute(\"data-secret\"))t=Math.random().toString(36).substr(2,10),e.src+=\"#?secret=\"+t,e.setAttribute(\"data-secret\",t);if(r||a)(t=e.cloneNode(!0)).removeAttribute(\"security\"),e.parentNode.replaceChild(t,e)}}}}(window,document);\n\/\/--><!]]>\n<\/script><iframe sandbox=\"allow-scripts\" security=\"restricted\" src=\"https:\/\/haneda-st.com\/example\/concert.html\/embed\" width=\"600\" height=\"338\" title=\"&#8220;Concert&#8221; &#8212; \u7fbd\u7530\u30b9\u30bf\u30b8\u30aa  HANEDA ENTERTAINMENT STUDIO - Tokyo Japan\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\" class=\"wp-embedded-content\"><\/iframe>"}