> Only in the case of Firefox is it really third-party code; both Chrome, Edge, and Safari ship with the EME modules developed by the respective companies, but they still sandbox it.
They still sandbox it because from the user's perspective it's still an unauditable black box, so at least the user can verify the sandbox. But that doesn't actually solve the problem, because the black box code is interacting with black box hardware. If there is a bug, you've done the opposite of sandboxing it -- you've prevented it from being traced and given it direct access to hardware.
> and dropping Flash without providing a replacement for encumbered video isn't an option: breaking websites like Netflix will cause users to use other/older browsers that do support Flash
The solution to Flash should have been to have someone reverse engineer it and publish a 100% open source implementation, including the DRM. Then let them keep publishing using Flash format as long as they like, but no more black box.