I don't recall this type of situation happening back in 2.0, but I do recall a time when walking by a market board would have your character spend over 3 million gil on a bone chip.
Printable View
They need to do better securing the client, or portions of it, at least, and securing the comunications between client and server. Validation on the server side would work, but it creates a large load that the server has to cope with in addition to everything else.