Crossdomain ajax request to controller with requireAjaxRequest()
Looking further into the problem, I've found that the page tries to do a post request to the other domain. It calls upon the action function in the UsersController.php file (Location: /craft/app/controllers/)

But because the user isn't logged in on the other domain and anonymous access isn't allowed for this action. You get redirected to /login to login on that domain.

https://craftcms.stackexchange.com/a/12268/635

The developers managed to solve this problem? This applies to almost all controllers require session.