How do BW browser extensions detect password changes?

Can someone explain how the Chrome extension autosave detects password creation/changes?

If it is well documented enough, websites might be more inclined to support it.
I suppose are 2 ways

  1. Normal simple POST

What attributes/names/headers does the extension use to activate the autosave banner?

I don’t know the answer to this, but when I want to find this type of information, I’d usually go poking around the codebase to look for clues:

I did but couldn’t locate it.

I would check out the following: