Detailed on my blog: Ajax with FormData is Broken on IE10 / IE11 in Some Conditions
You can change
action attribute of the form to send to a web server running in localhost and eavesdrop the request in a local proxy software like mitmproxy or Fiddler.
Add a hidden input with arbitrary name at the end of form, to make the original checkable input not the latest one.
I've opened a bug on IE Feedback.
Author: @yorkxin; Original Bin: http://jsbin.com/muqem/latest