I've got a payment system that won't redirect to paypal because of the error: "Refused to display document because display forbidden by X-Frame-Options." The form is posted and the proper redirect url is made, but there is no response returned from the paypal queries:
This redirects properly to the next query: https://www.sandbox.paypal.com/webscr&cmd=_express-checkout&token=xxx
This shows no response: https://www.sandbox.paypal.com/us/cgi-bin/webscr?cmd=_flow&SESSION=xxx&dispatch=xxx
If I cut and paste the first query into the browser, it redirects to paypal, when running from the application (in Chrome) however, I get the X-Frame-Options error. (or in Firefox, nothing)
This means that Paypal doesn't allow you to use Paypal in an iframe. You should not use Payapl in an iframe.