Really, most shared hosting environments have glaring security problems. Apparently it's been incredibly hard for Linux developers to create for an environment where shared hosting users can be definitively jailed into their own environments without breaking anything crucial.

I've almost been booted away from two separate hosting companies with charges on trying to compromise their system when I've demonstrated (to their staff only) how I could do cross-account file writing on any 0777 CHMOD file see more in the system with a simple PHP file.