A bug is in existence that allows a user to get a black key without payment of NX or GP. The bug goes as follows:
1. Visiting the Nexon website through http://combatarms.nexon.net.nexcorp.tk/combatarms.nexon.net/
2. Clicking on "store" after logging in.
3. Visit the black key page.
4. The black key being spontaneously placed in the user's inventory.
... This should be fixed for people not to get black keys unless they pay for it.