A way of properly handling HttpAntiForgeryException in MVC 4 application

If you only have one or a few functions affected, creating a filter might be slightly technical overkill. A simpler but non generic solution is to simply remove the [ValidateAntiForgeryToken] for the specific method and add a manual validation after checking if the user is logged in.

if (User.Identity.IsAuthenticated)
{
    return RedirectToAction("Index", "Home");
}
System.Web.Helpers.AntiForgery.Validate();
/* proceed with authentication here */