apple wants to make changes

What does the popup say? If it is a warning about 32 bit apps then it is likely legit. If it is asking for your financial and personal information it is not legit.

Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams - Apple Support

It's malware/adware being installed by the user. A Trojan.

Yes, MalwareBytes will still remove it after the trial period, no matter how many times you reinstall the malware. The only thing that changes with MalwareBytes after the trial period is the real-time protection against (mainly) ransomware turns off.

It's adware/malware, and a somewhat old one now.

Download and run MalwareBytes for Mac. It can detect and remove that one.

The common recommendation is for a Mac user to download MalwareBytes to clean up the phishing popup problem. No one seems to know how the malware actually gets into a system, however. That means that you can easily get reinfected again and again until the 14-day free trial of MalwareBytes expires. The "Apple wants to make changes" malware seemed to be fairly basic in that it somehow installed an app and added an extension to your browser. It has appeared under the aliases of SourceAdd, HelperPages, FormalSearch, and CoordinatorPlus. If you delete the app, remove its browser extensions, and track down any other associated files, the popup will go away, but then will reappear a couple of days later under a new name. This is really sophisticated behavior. Today, the popup came back yet again, but this time with no new suspicious app installed. Can MalwareBytes handle that?