Installed the 8.1 update yesterday, and IE immediately broke form submissions on a number of sites I frequent. As best I can tell, it’s making a GET instead of a POST to forms that have no elements beyond the actual submit button.
MVC apps in particular react in an expected way: They return a 404 on action methods that have [HttpPost] on them.
- Go to http://popforums.com/Forums and create an account.
- On the page, after you’ve signed up and are logged in, click the button "Mark All Forums Read." This is a form with no other elements that does a POST to /Forums/Forum/MarkAllForumsRead
- The server returns a 404 for the post URL, because it made a GET instead of a POST.