It's not an outside vulnerability; I reckon it really matters if you are on shared hosting, and you can't do much about it but nag your ISP.
(Unless your site - or any site on your server - was already compromised of course. In that case you're properly screwed, hehe. )
Edit: what makes it a far bigger issue is that Android, for example, is built on the flawed linux kernel...now on android you can just d/l an app and get screwed....