Something changed in the last few days that broke my apprequest code. I use MSFT's new Facebook SDK from https://github.com/Microsoft/winsdkfb which uses Xaml WebView to interact with Facebook via html. As of Friday, it started displaying a blank white page for apprequests. Copying & pasting the url into IE I get a 500 error page. Doing the same in Chrome results in a blank white page.
https://www.facebook.com/v2.1/dialog/apprequests?access_token=&redirect_uri=https%3A%2F%2Fwww.facebook.com%2Fconnect%2Flogin_success.html&app_id=&object_id=&to=&action_type=send&message=&data=
If I remove action_type & object_id, it works fine. Though obviously without the Graph object.
We had a bug that should be resolved now, here's the link: https://developers.facebook.com/bugs/862534523829812/