Phishing While Updating Applications

I think what you are seeing most likely is an attempted scam.

Did you provide any potentially damaging information to anyone? If yes, you'll need to follow up, for example, with a credit card company, Apple, your bank, etc.

If you gave you Apple ID password to a scammer, then

Change your Apple ID password https://support.apple.com/en-us/HT201355

Here is What to do [before] or after you change your Apple ID or password https://support.apple.com/en-us/HT204071

I doubt you account was compromised, but See If you think your Apple ID has been compromised https://support.apple.com/en-us/HT204145

 Also see:

Increase the Security of your Apple ID https://support.apple.com/en-us/HT201303

iCloud security overview  https://support.apple.com/en-us/HT202303

Ways to keep your information safe on Mac https://support.apple.com/en-gb/guide/mac-help/mh11402/mac

FYI: 

 See If you see apple.com/bill, itunes.com/bill, or an unfamiliar charge on your statement https://support.apple.com/en-us/HT201382

See Identify legitimate emails from the App Store or iTunes Store https://support.apple.com/en-us/HT201679

See How to avoid scams when using Apple Pay to send and receive money https://support.apple.com/en-us/HT208226

For scam related information from Apple including reporting scams to Apple see Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams https://support.apple.com/en-us/HT204759

I think changing your password is a good idea. See

Change your Apple ID password https://support.apple.com/en-us/HT201355

What to do after you change your Apple ID or password  https://support.apple.com/en-us/HT204071

I don't think there is a need for a complete wipe.

I don't know about: "How do I track down where the malware is on my computer network?" You might want to notify Apple. See the last link in my original post.

Yes