Fyrd/caniuse — pull request #404 by MartinanderssonDotcom (2013-12-26 15:41:57+00:00)
Title: Added IE bug #781303

IE10+ will consider two resources to be of the same origin and not make a CORS request with an Origin header added to the request if port is the only difference of the resources. This behavior goes against the specification and the behavior of all other modern browsers.