I was integrating a JQuery plugin for file uploads, uploadify, in my app when I saw a very strange behavior. The plugin reported an error transmitting the file to the server and debugging the controller code I noticed the target action wasn’t being called at all. Debugging the client code I found out that the server was redirecting the upload to the login page. The Controller was marked with the AuthorizeAttribute but the user was already authenticated. After a google search I found this article...