How can I get the contentWindow.location of the iframe, where the iframe src contains different domain name?

How can I get the contentWindow.location of the iframe where the iframe src contain different domain name? I have googled about this, but I found something like proxt, so how can I get the location of the window开发者_JAVA百科 inside iframe where iframe src is not on the same domain?

Browser-side XSS rules prevent the access and display external URLs in contentWindow.location. You can't do this.