1. The cookie value does not change, when a user logs in their cookie is the same each time, so it can be replayed.
2. Logging out does not invalidate the cookie on the server. It makes it so the user no longer sends the cookie, but manually adding the cookie to the request allows access.
These two issues combined are pretty serious, but before I inform my client, I was wondering how difficult it would be to determine the encoding algorithm used for the cookie. Due to the nature of the site, all userids are public, therefore if you could figure out the algorithm you could log in as any user.
But I don't know anything about encoding algorithms. Can anyone here decode these cookies, or point me in the right direction (or let me know if it's hopeless trying) on how to try to determine the cookie generation algorithm?
Here are two cookies and their corresponding userids:
Any help would be greatly appreciated. Thanks.