Najafi Q&A: theft

If a person is known to steal and works for someone, is it permissible for someone who knows about this to inform the employer of the worker's character, especially if they know the person has not repented, or if they are unsure whether the person has repented?

If a person steals a book or takes it without the approval of a competent authority. Then, he obtains knowledge from this book. In both cases, is there a religious problem with the knowledge obtained?