YOU had a spyware virus. In fact, it was embedded in the screen capture you posted, which is why I removed it. It is a trick to get you to download their "anti virus" program which is, of course the virus itself. I use a fully protected Mac and got the same "message" which is how I know it was a trick.
It has nothing to do with our Forum. You have to log out of the Forum and shut down your browser, then restart and log back in to remove the problem.