To disable Mozilla’s data grab, enter:

about:preferences#privacy

in the address bar.

Then, scroll down to “*Web Site Advertising Preferences” and DESELECT the option for “Allow websites to perform privacy-preserving ad measurement”

Credits to @funnymonkey@freeradical.zone

**Update: **Im deutschen nach “Werbeeinstellungen für Websites” suchen und “Websites erlauben, datenschutzfreundliche Werbe-Messungen durchzuführen” abwählen.