The way you've described it, sounds like a cross domain cookie. That isn't technically a thing unless you consider one domain/company selling the tracking of t

The way you've described it, sounds like a cross domain cookie. That isn't technically a thing unless you consider one domain/company selling the tracking of their cookie for you to another domain/company or a data broker/aggregator. So it sounds like it could make tracking of activity much easier and that doesn't sound right.