Tell them when they hire you, you will help them.

I made the mistake of talking too much. Not that I was letting out valuable secrets, but I helped them understand how they were looking at it completely wrong. They had made the proverbial mountain out of a mole hill. They made me a non raise offer. I did not give them reason enough to need me.

You also have to consider if answering would violate your sense of morality.

Ask them if they do this stuff within their own engineering teams. If they don't, this is then your cue to leave the interview.