get the URL of an iframe’s parent page, via Nicholas Zaka's article - http://www.nczonline.net/blog/2013/04/16/getting-the-url-of-an-iframes-parent/

getParentUrl.js

function getParentUrl() {
    
    var isInIframe = (parent !== window),
        parentUrl = null;

    if (isInIframe) {
        parentUrl = document.referrer;
    }

    return parentUrl;
}