Facebook is fake rumor central. Example: Jayden K. Smith the hacker. That one has been kicking around since 2009. When someone forwards you a message warning about some dire evil on Facebook, and asks you to pass it on, why not take a minute and type it into Google and see what comes up.
I used to send people to Snopes, but they have taken a strong political tone lately that makes me uncomfortable. factcheck.org does equally well at busting rumors and fake news. Or simply ask your favorite search engine if a rumor is true.
But please: check before you pass on that warning. Your friends will thank you.