Betting on what people say is becoming an increasingly popular category of prediction market sites. Now, federal officials have opened a probe examining whether those markets are a magnet for manipulators.

Betting on what people say is becoming an increasingly popular category of prediction market sites. Now, federal officials have opened a probe examining whether those markets are…

The CFTC is reviewing prediction betting platforms' so-called mention markets, people familiar with the matter confirmed to CNBC.