Please, can anybody check level 15 -- euid is dropped in all cases:

level19@erebus:/vulnerable/crypto$ ls -l challenge
-r-sr-xr-x 1 level15 users 8003 2007-09-02 23:10 challenge
level19@erebus:/vulnerable/crypto$ ./challenge
Encrypted string: TOEIXEBTWAYKZASU
Decrypted string: SPDJWFAUVBXLYBRV
level19@erebus:/vulnerable/crypto$ id
uid=1010(level19) gid=100(users) groups=100(users),1009(level19)

Decrypted string seems correct, no failure message like

level19@erebus:/vulnerable/crypto$ ./challenge
Encrypted string: QSQTBEYQSSAOSAZN
Decrypted string: xxx
You fail!