In a way this post is mislabeled, because it’s not really WordPress and more a case of badly set permissions..
Anyway, if you’re using WordPress or ANY script that involves permissions set to 666, you need to get them changed to 644 now. Erm, I think it’s 644 anyway. Folders need to be set to 755. If you don’t know how to change file permissions, google it, because I’m still too lazy to write a tutorial on it.
Tell your friends.