I have a re-occuring problem with the Flash Installer on my Dad's Mac.
Flash Player was successfully installed onto the MacBook Pro quite a while ago, and it is currently up to date with the latest version. However, the 'Flash Player Installer' is still on the
desktop (screenshot attached).
We have tried everything, even uninstalling and reinstalling. When we reinstalled, a separate 'Flash Player Installer' opened alongside the original one.
Recent versions of MacOS reopen windows for you because it's convenient or something. I think it's a really confusing user experience, and rarely what I want the system to do. I'm primarily a Mac user at this point, and it totally freaks me out on a daily basis.
Anyway, do the following:
Open Finder and eject the Adobe Flash Player disk image from the left-hand column, if it's still mounted.
Then log out of the machine, but uncheck the "Reopen windows when logging back in" on the logout dialog.