Why am I receiving a message from Adobe Flash saying "Your Mac Might be Infected"?

I clicked on a link and received a message that I needed to update Adobe Flash. When I clicked to do the update, I received a message saying "Your Mac Might be Infected." On the same page, it gives instructions to remove any possible infections using Mac Cleaner. I haven't done anything because I don't know if this is real or a hack. Has anyone else seen this and followed through on it?