If you are on shared hosting and Register_globals are on by default at the server level. and your php is 4.3.2 or later,. then you hosting provider has broken php.net's recommended settings of register_globals off and has even changed the default setting to On.

this allows any site on that server to be exploited and gain full access to all sites and accounts on that server. this is your hosting companies fault, and their blatent abuse of their customers trust in not providing safe secure hosting see more by following php.net's recommended settings for Register_globals