Why is OnAuthorization called twice in my custom AuthorizationFilterAttribute?

Question

Why is OnAuthorization called twice for my straight forward AuthorizationFilterAttribute?

public class ApiAuthenticateAttribute : AuthorizationFilterAttribute
{
   public void override OnAuthorization(System.Web.Http.Controllers.HttpActionContext actionContext)
    {
        if(NotAuthorized())
            throw new Exception();

    }
}

First Call Stack

Second Call Stack

Answer 1

The problem was with Ninject.Web.WebApi. For some reason it was registering the filter twice. Updating the package to latest (v 3.2.1) fixed the issue.