he may have sent the PM to multiple people...
Correct. Everyone calm down. I am not even 100% sure if the developers haven't already thought of it and have mitigation already in place.
Relax while we work through it. I doubt it will take a long time.
Why bother selling the exploit if you could use it whilst having a short position in Monero?
Or better yet, prove it and steal all the funds, you'll likely make off with far more than 100 bitcoin before the exchanges shut down.