If you look at the Mac security updates lately, you can see avalanches of "execute arbitrary code" fixes for every release. It seems that Mac Os X has more holes than a factory of Swiss cheese.
EDIT:
Why was this downvoted?
If you down vote at least you can comment why.
These are the security updates since Oct:
That's the problem with C, it can't be written securely and these bugs will continue to be fixed for decades.