> But if the user was going to do this anyways (flash some unvetted binary to their device), the web still provides MORE security than having the user download flasher.exe + badbinary.elf
I've very very often heard people complain (even some in this very thread!) that you can't get people to (or people outright refuse to) download programs and run them if they're not delivered by Steam or similar. I've also very often heard people complain that ordinary users of web browsers will click anything and everything standing between them and what they want to do without either reading it or bothering to think about what they're doing it.
Given these two points, I'd argue that giving direct access to USB devices to any random website is (from a security standpoint) disastrous for the average user. A user who clicks the "Yes, give access to this USB device to 'website.com'" prompt is almost never going to intend to -say- flash the firmware on that device... and would almost never have any idea if it was or was not possible to do so.
I've very very often heard people complain (even some in this very thread!) that you can't get people to (or people outright refuse to) download programs and run them if they're not delivered by Steam or similar. I've also very often heard people complain that ordinary users of web browsers will click anything and everything standing between them and what they want to do without either reading it or bothering to think about what they're doing it.
Given these two points, I'd argue that giving direct access to USB devices to any random website is (from a security standpoint) disastrous for the average user. A user who clicks the "Yes, give access to this USB device to 'website.com'" prompt is almost never going to intend to -say- flash the firmware on that device... and would almost never have any idea if it was or was not possible to do so.
Relatedly; apparently even Google has locked down WebUSB because it substantially weakened client security: <https://news.ycombinator.com/item?id=43362586>.