Well unless your post goes something like "Hi, I work for Apple and we're releasing this X in 3 months and I need to make sure features Y and Z work with Cocoa" I wouldn't really worry about the bit about releasing information you shouldn't.
More to the point, I think you'll find that people rarely (if ever) copy and paste code directly from something commercial. For one thing, it's rarely appropriate. There'll be a lot of stuff in there that's just not relevant to the question. A good question will have reduced such code to a small test case, in which case it no longer resembles the original code.
Likewise the answer will be for the simplified problem, not for your code, so copying and pasting it verbatim is (imho) unlikely.
The value in SO answers is in helping you understand the problem and finding a solution. You then apply that solution to a similar (but ultimately different) problem at work.
Now if that solution has a problem in it, you have two safeguards. Firstly, it will hopefully get downvoted. That doesn't always happen but it usually does. I've seen bad answers get upvoted. The second is that you are ultimately responsible for any code you produce at work. So you can use something you found on the net but by putting it in you are using your professional expertise to vouch for its efficacy, robustness and appropriateness.