Earlier quoted context omitted.
In the past, browsers used an algorithm which only denied setting wide-ranging cookies for top-level domains with no dots (e.g. com or org). However, this did not work for top-level domains where only third-level registrations are allowed (e.g. co.uk). In these cases, websites could set a cookie for .co.uk which would be passed onto every website registered under co.uk. Since there was and remains no algorithmic meth…
All web encryption is backed by static list of root certs each browser maintains. Idk any other way to solve it for the general public (ideally each user would probably pick what root certs they trust), but it does seem crazy.
This solution is even more obvious today where most certificates are just DNS lookups with extra steps.