/usr/lib/firefox-esr/defaults/pref/channel-prefs.js is in firefox-esr 52.8.1esr-1~deb8u1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 | /* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
pref("app.update.channel", "default");
|