Like 6 months ago, when I was still a GM, there was this mass hacking were like 40 ppl were hacked in just one day. Password changed, items stolen/deleted, coins stolen. This happened like 3 days in a row. ppl from all servers in a matter of seconds.
Password was the same for all the ppl hacked in the same day. Some were even ingame. When we looked the IP, the same IP showed in all accounts. Same password, and same pattern (no coins, no items not even pots).
411, Forsete, Uarehistory and lots of high level players were hacked and completely striped. Guess was some sort of attack that mass changed passwords for all those chars in matters of seconds and then ppl in a LAN center started to steal their shit cause K2 had to IP ban to make this stop.
Months later, almost all lvl70's char from diez got hacked too. IP matched all characters. Stories like this go on and on. As u can see, this is not someone sharing his account.
These are clear cases of sql injection, db hacking or exploiting security holes in the website. This still happens and the only difference is that hackers noticed there's little benefit on stealing someone's item when u can create a GM account instead and farm legit items. Its quiet and doesnt draw attention to them. Why hack someone else when u can farm and get even better items and nobody will know/complain about it? GM commands are not a secret anymore. Lots of ppl know how to use a GM account, how to move arround, spawn bosses and farm. By the time K2 notices there are more GMs than the ones created by them, its too late and items are spread in hundreds of different accounts, ready to sell on ebay.