• A user.js file is an alternative method of modifying preferences

server# FIREFOX_USER=user2

server# cat /home/${FIREFOX_USER}/.mozilla/firefox/$(grep 'Path.*esr' /home/${FIREFOX_USER}/.mozilla/firefox/profiles.ini | cut -d'=' -f2)/user.js

user_pref("network.proxy.http", "gate");
user_pref("network.proxy.http_port", 3128);
user_pref("network.proxy.type", 1);

Помогает:

about:config

network.auth.use-sspi;false