I recently found out, that a 3rd party software has appeared to work with Tera clients. It is worse than L2's Ranger, even though it works with scripts as well, but Tera's client lacks any kind of security.
The bad thing with that is that both NA publisher EnMasse and EU publisher Gameforge are unable to combat it, if the Korean dev doesn't address the security of the game client. The software appeared December 2016.
It all started by the efforts of a player who was trying to addressing the latency issues between client and server and fps drop, since both are quite significant in an action combat system like Tera. He manage to develop a software that could interfere between client-server packets. The problem was that it was distributed freely, and that open the road for others to jump in and start making proprietary scripts that could do much more than addressing the latency issues and skill lag for example.