Pasted

Type about:config into the URL textbox and set the following:
 network.proxy.socks_remote_dns    true
network.dns.disablePrefetch       true
network.dns.disableIPv6           true
 This way Firefox will resolve host names via tor, which prevents DNS leaks.
 media.peerconnection.enabled    false
 This prevents leaking the system ip address through WebRTC requests.