http://en.wikipedia.org/wiki/Exploit...line_gaming%29

Game mechanics
Taking advantage of the systems that make up the gameplay. A game mechanics exploit is not a bug—it is working as designed, but at the same time is not working as intended.
http://www.thefreedictionary.com/exploit

Simply put, the players are taking advantage of a poor game design in a way that was not intended.

Thus it is an exploit. No ’if’s, ’and’s or ’but’s about it.