When you trust someone to keep a secret you would hope that they will not tell anyone what you told them in confidence. But, if they do share your personal information immediately tell them so. Explain to them why you did not appreciate them spilling too much information and that they have broken your trust. If they tell you not to worry about it, persist and tell them you have every reason to worry since you did not want to information shared with everyone. If you hear someone sharing personal information about someone else, correct them as well.