Very little code is bullet-proof. Hackers will always find holes. The worst holes will be critical. The worst hacks will be zero-day and found in the wild -- catching companies and users both by surprise.
Not sure we have any of that here. Macworld does report that, at the Black Hat Europe Security Conference, former NSA number cruncher Charlie Miller -- who has rolled his ability to find exploits in the Mac version of Apple's Safari Browser into tens of thousands of dollars and a couple free MacBooks at the annual Pwn2Own contest -- claims to have: