핸드북:Firefox
Revi HQ
DNS over HTTPS
Security measure to counter the attacks from South Korea Government DNS MITM attacks.
about:config
network.trr.mode
=>2
network.trr.uri
=>https://cloudflare-dns.com/dns-query
network.trr.bootstrapAddress
=>1.1.1.1
Then restart Firefox to double check it's using DNS over HTTPS.