/usr/lib/firefox/defaults/pref/all-ubuntumate.js is in ubuntu-mate-default-settings 18.04.17.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | pref("general.config.obscure_value", 0);
pref("general.config.filename", "ubuntumate.cfg");
|