Clipboard, browser extension, or universal autofill for macOS web pages - which is safest

1P_Evon , thanks for those links. The browser one added some useful information.

I want to know about the relative risks between the three approaches. Is there a link that discusses that?

I suppose that a very detailed security analysis of the three approaches would allow a professional to arrive at an opinion of the relative risks. But, even if I were to study the three approaches, I am not knowledgable enough to form that opinion myself. It seems well beyond anyone but a security researcher to do that.

As an example of my naivety, I suspect that using the clipboard is the worst choice. Leaving even a portion of my credentials on the clipboard for 90 seconds, exposes it to all potentially untrusted applications on my computer. But, I don't really understand that risk. For example, can a background process receive an event of something arriving on the clipboard and read it (something that is not triggered by user activity).

So, you can see, I'm not equipped to evaluate things. Knowing that the clipboard is cleared in 90 seconds adds almost nothing to my understanding.