MacOS – Stop Safari (MacOS) from suggesting password on captive portal

alright I may have some light to shed on this:

I just got off the phone with an Apple Engineer and he said a few things to me that make sense. He has stated that the "crippled browser" should never be displaying any other page than our captive portal page. He stated that if after logging into captive portal I am redirected to www.apple.com/library/test/success.html the iPad's "crippled browser" will close. If I see another page (like I saw apple.com and not http://www.apple.com/library/test/success.html which would have closed the browser.) it is likely that the system hosting captive portal is not directing me to the exact original page requested. Which was http://www.apple.com/library/test/success.html It could in fact be truncating or altering the original URL, which is possibly why I see apple.com's main page in the "crippled browser"

No resolution yet, as I still need to confrim that the wireless controller is indeed doing this, but it makes sense, and might help.

As one can see you have the "Remember Networks this computer has joined" Enabled.

When you join new network, that information is saved in the

com.apple.airport.preferences.plist

located in SystemConfiguration folder.

Obviously iCloud gets that file.

EDIT

Since you asked a new question and want to know how iCloud does that read this. (and click on User defaults database to expand)

Designing for Key-Value Data in iCloud

To store discrete values in iCloud for app preferences, app configuration, or app state, use iCloud key-value storage. Key-value storage is similar to the local user defaults database; but values that you place in key-value storage are available to every instance of your app on all of a user’s various devices. If one instance of your app changes a value, the other instances see that change and can use it to update their configuration.

and