Hilchos Rechilus, chapter 5, section 3

However, if you see from the start of the story that listening may protect you from physical harm or loss of money, you may listen. You may also suspect that it might be true, as in the Laws of Lashon Hara (p. 56). But the Torah forbids believing the story. To see the best way to act, see the Laws of Lashon Hara above (p. 58).

29) If you see clear signs that someone wants to harm you, in body or in money, you may ask people about it in order to protect yourself. This is true even if nobody told you anything about it. You do not need to worry that this will lead people to speak badly about him.