Firefox updates the black- and whitelists for Tracking Protection daily using a domain that might not only occur on some Blocklists, but also can be blocked as the result of regex blacklists for starting with “tracking”.

The domain should be whitelisted to ensure the Tracking Protection can be updated (when used at all), or it might render some websites useless on the Firefox Webbrowser in the long run.

tracking-protection.cdn.mozilla.net