Its patched, but you used to be able to max the flag capture limit at 140-14000, and just capture 1 then leave the room. The person who didnt leave would get up to 4000 EXP, and it took like 1 minute MAX. The GM hack way was a simple string search, and the level hack was a packet edit. That looks like he packet edited, or he was using the EXP Hack with MHS or a UCE, where you could edit your client side EXP.
EDIT***: Thats packet editing, notice how he doesnt get the client sided "Level Up" sign beside his name, which would mean he is editing his client side EXP with MHS.