Is "Mac Cleanup Pro" legitimate or a scam?

Mac Cleanup Pro is malware and should not be downloaded. Applications/programs you download can’t open or run themselves without you authorizing them to first. I wouldn’t think too much about it if you have not opened the file.

https://www.pcrisk.com/removal-guides/13775-mac-cleanup-pro-unwanted-application -mac

Never download Flash Player from anywhere but the Official Adobe website or from within System Preferences > Flash Player > Check for updates. There are many bogus Flash Player installs that will install malware.

Mac Cleanup Pro is not Apple. No Anti-Virus software or so-called “cleaning” apps are needed or recommended for Mac OS. They can conflict with Mac's own built-in security. At best they will slow your Mac by using unnecessary resources and at worst will bork your entire system.

If you think you have installed malware run Malwarebytes. Malwarebytes was developed by one of our own colleagues here in ASC and is about the most proven anti-malware software for Mac.

Ah, ok. It’s a shame that these “hackers” leech off of Adobe’s Flash Player to wreak havoc inside victim’s computers. Adobe Flash Player used to be so popular back in the day, so that made it an easy target for hackers. That’s my theory on why there are so many of these scams.

Actually, these types of downloads can deliver the malware within the installer for the Flash Player. So while you think you are authenticating for Flash Player it will also install the malware.

Yes it was, but Flash Player has now been mostly replaced by HTML5 and there are very few sites left that still use it.