Tags: pwnable 

Rating:

Fawkes has been playing around with
Finite State Automaton lately. While
exploring the concept of implementing
regular expressions using FSA he thought
of implementing an email-address
validator.
Recently, Lua started to annoy Fawkes. To
this, Fawkes, challenged Lua to a battle of
wits. Fawkes promised to reward Lua, only
if she manages to transition to a non-
reachable state in the FSA he implemented.
The replication can be accessed here.

Original writeup (http://geeksspeak.github.io/blog/2015/04/03/backdoor-ctf-2015-forgot-writeup/).