Firefox

I hope that the rest of the space including the W3C sticking to their guns and opposing Web Environment Integrity prevents this from doing too much damage, but Chrome's monopoly is already at such an extent that many websites only test on Chrome, and a few outright require it. As long as this is implemented in Chrome, and if people who use it get more return from ads as the proposal suggests, some websites will be willing to implement it.

This is definitely seeing more and stronger opposition than the Encrypted Media Extensions proposal, but my fear is that it will go in that direction; if big websites implement it, Mozilla, Vivaldi, and W3C will eventually cave despite their initial opposition.