The point of the attestation is to show that given browser won’t do some things. If the browser is open source on open source operating system the user can modify it in any way he wants, so not such attestation can be given to such browser.
Even if we are ok with attested browser being official builds never modified by users, then user could still fake it if they have full control of their operating system. So the operating system must also be attested, so it cannot be freely modified. And what is a point of open source then? You can see, but you cannot touch?
The point of the attestation is to show that given browser won’t do some things. If the browser is open source on open source operating system the user can modify it in any way he wants, so not such attestation can be given to such browser.
Even if we are ok with attested browser being official builds never modified by users, then user could still fake it if they have full control of their operating system. So the operating system must also be attested, so it cannot be freely modified. And what is a point of open source then? You can see, but you cannot touch?