Replying to
@slightlyoff@toot.cafe @jaffathecake@mastodon.social But autofill sync is a feature for the Firefox user, that the website authors don't directly interact with, right? So the ToS is solely between the end user and Mozilla.
Here we're talking about a website author possibly infringing a ToS depending on the web browser being used. If the prompts were always user input, then that would be the end user infringing the ToS, but AFAICT this is not how the Prompt API is designed and no guarantee could be made about the source of the prompts.