autocookie | Automatically load stolen cookies from ChromePass | Security Testing library

I have an MVC application that uses Active Directory membership for user authentication.

After the user logs in, a FormsAuthenticatedTicket is created and encrypted. Then, in Application_PostAuthenticateRequest the ticket is decrypted and the deserialized user data is stored in a custom principal object.

i have changed the expiration date of ticket from AddMinute(30) to AddMenute(10)

My problem is that when a user logs in after their cookie has expired, the ticket is encrypted with the current login data, but in global.asax the previous login's ticket is still decrypted. When debugging, I have seen the ticket data of the previous expiration date (after 30 minute not 10 minutes) of the same user with ticket version decrypted to 2.

What mistake did I make?

Edit : i resolved this problem with removing FormsAuthentication.SetAuthCookie(userName, rememberMe); because i have used the FormsAuthenticationTicket object

but I am in front of another problem: in global asax Application_PostAuthenticateRequest, when trying to reading the cookie, i have found by debugger that's null although the cookie added with ticket encrypted successfuly