user_pref("network.proxy.backup.ftp", "");
user_pref("network.proxy.backup.ftp_port", 0);
user_pref("network.proxy.backup.socks", "");
user_pref("network.proxy.backup.socks_port", 0);
user_pref("network.proxy.backup.ssl", "");
user_pref("network.proxy.backup.ssl_port", 0);
user_pref("network.proxy.ftp", "127.0.0.1");
user_pref("network.proxy.ftp_port", 3090);
user_pref("network.proxy.http", "127.0.0.1");
user_pref("network.proxy.http_port", 3090);
user_pref("network.proxy.share_proxy_settings", true);
user_pref("network.proxy.socks", "127.0.0.1");
user_pref("network.proxy.socks_port", 3090);
user_pref("network.proxy.ssl", "127.0.0.1");
user_pref("network.proxy.ssl_port", 3090);
user_pref("network.proxy.type", 1);

user_pref("network.proxy.backup.ftp", "");
user_pref("network.proxy.backup.ftp_port", 0);
user_pref("network.proxy.backup.socks", "");
user_pref("network.proxy.backup.socks_port", 0);
user_pref("network.proxy.backup.ssl", "");
user_pref("network.proxy.backup.ssl_port", 0);
user_pref("network.proxy.ftp", "127.0.0.1");
user_pref("network.proxy.ftp_port", 3090);
user_pref("network.proxy.http", "127.0.0.1");
user_pref("network.proxy.http_port", 3090);
user_pref("network.proxy.share_proxy_settings", true);
user_pref("network.proxy.socks", "127.0.0.1");
user_pref("network.proxy.socks_port", 3090);
user_pref("network.proxy.socks_remote_dns", true);
user_pref("network.proxy.ssl", "127.0.0.1");
user_pref("network.proxy.ssl_port", 3090);
user_pref("network.proxy.type", 1);
user_pref("media.peerconnection.enabled", false);
user_pref("browser.safebrowsing.malware.enabled", false);
user_pref("browser.safebrowsing.enabled", false);
user_pref("network.dns.disablePrefetch", true);
user_pref("network.dns.disableIPv6", true);

Update Firefox profile: Disable WebRTC, DNS prefetch and IPv6, safebrowsing; Enable socks remote DNS