Every copy of Firefox is personalized: https://www.ghacks.net/2022/03/17/each-firefox-download-has-a-unique-identifier/

@mckinley@mckinley.cc Wow! 😱

This data will allow us to correlate telemetry IDs with download tokens and Google Analytics IDs. This will allow us to track which installs result from which downloads to determine the answers to questions like, “Why do we see so many installs per day, but not that many downloads per day?”

Also wtf?! 🤦‍♂️ #EvilTracking