If they would simply get rid of all HTML submissions pages where users may enter their passwords, then the system would probably acceptable. If the Firefox Acc

If they would simply get rid of all HTML submissions pages where users may enter their passwords, then the system would probably acceptable. If the Firefox Account UI were entirely browser-managed, it'd be okay. I'd still prefer a system in which it's impossible for users to accidentally leak their secure data through use of a poor password, but that's life. As an aside, I don't see that user key management was really an issue. The UI of the old system was perfectly fine, and one could have added a QR code or similar if one really wanted to. The number of folks doing TOTP auth these days prove that it works. There's only one reason to use dynamically-downloaded JavaScript to ensure user privacy: because one wishes to silently and undetectably undermine user privacy at some point in the future.