Iconomy hack?

There is a guy who came in a server which have Iconomy plugin and then started to giving other people millions and millions of money. What is this hack?

Mybe wrong permissions ?

iConomy can't really be hacked, unless someone has a very advanced client-server modifier. iConomy data is stored server-side, either in an SQL file, database, flatfile or something else of the millions of storage options iConomy has.