You probably have no recourse at all. Whether or not what the prospective employer did was moral, fair, professional, etc., there is no law against employer A telling anyone, including employer B, that an employee of B is interviewing with him. This is simply not information that someone is obligated to keep confidential (unless and only to the extent that the prospective employer may have agreed, preferably in writing, to hold the information confidential). This is a known risk of interviewing while employed; while it is very unfortunately, it does happen. Since there is no general duty to keep the identify or fact of interviews condidential, there is no ability to take legal action against someone for disclosing it. In the future, do not interview with someone who knows your current employer--that's the best way to avoid this.