MVC 4 provided anti-forgery token was meant for user “” but the current user is “user”

Question

I\'ve recently put Live a web application which was built using MVC 4 and Entity Framework 5. The MVC application uses

Answer 1

I had the same problem when

• User logs in
• Then on the Home Page the User hits Back Button to go back to Login
• User logs in as a different User
• This gave the exception : The provided anti-forgery token was meant for user "" but the current user is "user"

I found this was happening only in IE and I fixed it by doing a couple of things

1. Disabled output caching for the login page, because in debug mode I found that hitting the back button did not generate a new request to the Login page

2. On the login page I added a check to see if the user is already authenticated, and if so logged out the user, and then redirected to the Login page again.

   [AllowAnonymous]
   [OutputCache(NoStore=true, Location=System.Web.UI.OutputCacheLocation.None)]
   public ActionResult Login)
   {
       if (HttpContext.Request.IsAuthenticated)
       {
           WebSecurity.Logout();
           Session.Abandon();
           return RedirectToAction("Login");
       }
   
       return View();
   }
   

Answer 2

The validation code that runs against an AntiForgeryToken also checks your logged in user credentials haven’t changed – these are also encrypted in the cookie. This means that if you logged in or out in a popup or another browser tab, your form submission will fail with the following exception:

System.Web.Mvc.HttpAntiForgeryException (0x80004005):
The provided anti-forgery token was meant for user "", but the current user is "SomeOne".

You can turn this off by putting AntiForgeryConfig.SuppressIdentityHeuristicChecks = true; in Application_Start method inside Global.asax file.

When a AntiForgeryToken doesn’t validate your website will throw an Exception of type System.Web.Mvc.HttpAntiForgeryException. You can make this a little easier by at least giving the user a more informative page targeted at these exceptions by catching the HttpAntiForgeryException.

private void Application_Error(object sender, EventArgs e)
{
    Exception ex = Server.GetLastError();

    if (ex is HttpAntiForgeryException)
    {
        Response.Clear();
        Server.ClearError(); //make sure you log the exception first
        Response.Redirect("/error/antiforgery", true);
    }
}

More info:

Anti forgery token is meant for user “” but the current user is “username”

Html.AntiForgeryToken – Balancing Security with Usability

Answer 3

I believe this is occurring because the users are double-clicking the submit button on the form. At least that's EXACTLY the case on my site.

Troubleshooting anti-forgery token problems