I've signed a few, and they usually explicitly cover the details of the questions themselves. In other words, you can say you had to solve an algorithmic problem, but you can't mention the specific details or wording of that problem.

This is primarily so their questions don't end up on LeetCode or other practice websites; they always end up there anyway, so it really just slows down that process and prevents them from having to think up new questions quite as often.