badmedicine - DEFCON CTF quals 2013

Challenge description:

http://badmedicine.shallweplayaga.me:8042

This challenge greeted us with a simple username prompt.

Entering a username, it’s revealed that the task is to log in as the user admin. However, attempting to do so gives a message that admin logins are disabled.

Examining the cookies, we see that a cookie is set upon login. The contents are hexadecimal, and appear to be related to the username.

The hunch was then, that logging in as admin' and removing the last byte from the cookie would solve the problem, and it did.

The key is: who wants oatmeal raisin anyways twumpAdby