The Matt Riddle-WWE story is no secret to anyone but WWE still wants to keep a lid on announcing anything. Riddle is not allowed to say anything either but it's been clear for a week that he has signed a deal or will be signing one soon.
Combat Zone Wrestling announced that fans that attend their July 28th show will be able to see Riddle. The graphic says, "Don't miss one of Matt Riddle's final indy appearances before going to WWE!"
WWE probably won't be happy with that but this was likely done without Riddle's knowledge. Dave Meltzer of the Wrestling Observer Newsletter asked Riddle if he was going to WWE and no answer was given, obviously because he was told by WWE not to say anything before they make an announcement.
Riddle previously pulled out of PWG and OTT Wrestling in London and the belief is that he will be introduced during NXT Takeover: Brooklyn 4.