Chrome is sending top url of iframe

Suddenly Chrome is able to get the cross-domain url. Firefox is not able to do this.

I have got the following setup:

www.page.com/ads.htm

there is implemented a javascript code which is able to get the top url

this page is loaded by

page.com/frame.html (without www so that is hits the same origin policy)

where I have implemented a iframe which is showing to www page.com/ads.htm

at last page.com/frame.html is loaded in an iframe by

http://ift.tt/1LXEUJE

In the past the javascript code in ads.htm has been able to get only the page.com/frame.html. But suddenly Chrome is able to get the http://ift.tt/1LXEUJE. Firefox is not able to do this.

How can that happen and how can I avoid this?