All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
If such hacking violates the terms and conditions of the owners of the game and those who offer the vouchers; then this hacking is not permissible and the hacker does not have the right to take those vouchers because he does not deserve them. Allaah Almighty says (what means): {O you who have believed, do not consume one another's wealth unjustly.} [Quran 4:29]
Allaah knows best.