Firefox has had automatic security updates enabled by default since... forever. You just have to use Firefox for more than 2 minutes so you give it time to check the mozilla servers. Also, if you had been on top of things you'd know that Firefox 12 will even remove the need for an administrator account. Firefox 13 will then bring full silent updates without any user interaction at all. See wiki.mozilla.org/.../Silent_Update
Stop spreading FUD. It smells.