alt Hacker NewsYes? The cookie in question is First Party, which means you’ve consented to permitting only that party to track you using it, and not permitting its use for wider behavioral tracking across websites.
However, the locally hosted FB/Yandex listener receives all of these first party cookies, from all parties, and the OPs implication is (I think) that now these non-correlateable-by-consent first party cookies can be or are being used to track you across all sites that use them.
Not only did you only consent to the one party using it, but the browser has robust protections in place to ensure that these cookies are only usable by that party. This “hack” gets around the restriction completely, leveraging a local service to aggregate all the cookies across sites.