Starting today, Mozilla is activating the DNS-over-HTTPS security feature by default for all Firefox users in the U.S. by automatically changing their DNS server configuration in the settings. This privacy-focused technology makes it harder for man-in-the-middle attackers, including your ISPs, to manipulate DNS queries, eavesdrop on your Internet connection, or learn what sites you visit. Google took care of this privacy issue while announcing DNS over HTTPS feature in its Chrome web browser late last year.
Source: https://thehackernews.com/2020/02/firefox-dns-over-https.html