gistfile1.txt

function isFrameSafe(frameElement) {
    var origin = location.protocol + "//" + location.hostname;
    return frameElement.src.indexOf(origin) === 0
}

var iframe = document.createElement('iframe')
iframe.src = "http://www.facebook.com/ai.php?aed=AQLlH2cfdnsnLrDUVyqrQPlWpayw9N09Z_iNuhulevbeEfVa4mcVRcT8cjAZOjQb8y1QXab5Ae3aSEJx49U_Qv35rtSp1VC9cY0_CrpOjMDk40hS_Xm57A996YtRVCcWSuRZ_jZERQ_iA_E4621NAbKHT9dsB7uElkRtTvl5K-zPI0jeH-BEnlZIOXbeEdbRC6qCwoToaltolpe-Ot2KWgkfb_vBZYpzUc3jQoEHzLG6tauO9l_hkXpYpHxnt-KYFKIFZ1PgmrHgb0UcGjeKHl7yBR1AbW2n5XgdgaAhFvBjs5GZlKy566nvl8eLRA60orwkwtWYeN8-gKoAmOLm7-6minsWn8lk1h2Qn3p07HCTSnYHfv1aJ6mF5jmuzP0YYe7Ym9ZbmK-tvax4uPAQJ2OdULilKbEh8M-2V9pVY3AC228OPlrRullZuuOg8DI2A8WeMF-fbbOdOFFVCe5Gj1CaZu3LYXiqdG7mUgY6AEpk9ZzGT4fC2K8DInQo1AypCvzG64C_bEWfODeXe0aGbkWwsUUmO7E5HFg0tvZkK5IAR_xxxQ2rlf5jbcEDo_2gdIDdHe1HT75-SJLUsSA0M8EU01oNNPuWwEC2BW6inepc9QPuqeg42tcEbKLU-rIUnXDBLvgutft8azWPPQ6_LafGjCAmC9uTalagoWLLDMpQOThvPg7YeVd7qg_c9Mzn2GAfuswcxDSxyRIZo9MaOhA6mhfXeE1tmjyBBsMxnx08tO21Jsfgch59fmMxpeJzdsNMPK3FAojfglvCQ2Zrt_6ataexUB4xlM7_PhKrfBPtxb5fe2TE9-nlWruNEpoCrzI05yv4Go3CYEWHob06K_9iICfNVTFkSYGTiJnMXCy_fdgfyzUIn5QJIPRo4-Wnyg444zKAO_nyFW59LqbIanHVfFY6ybiA6KeC3meREWzTPSsrU5d_NbYHlJWb8uPNDR04jaH5e2qiYj3Y8qgLQA5m";
document.body.appendChild(iframe);

console.log(isFrameSafe(iframe)); // this prints true

iframe.contentDocument; // this throws an xdomain security error;