/usr/lib/firefox/ is in firefox-locale-br 28.0+build2-0ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/firefox-addons/extensions/
/usr/lib/firefox-addons/extensions/langpack-br@firefox.mozilla.org.xpi
/usr/lib/firefox/distribution/
/usr/lib/firefox/distribution/searchplugins/
/usr/lib/firefox/distribution/searchplugins/locale/
/usr/lib/firefox/distribution/searchplugins/locale/br/
/usr/lib/firefox/distribution/searchplugins/locale/br/amazon-france.xml
/usr/lib/firefox/distribution/searchplugins/locale/br/duckduckgo.xml
/usr/lib/firefox/distribution/searchplugins/locale/br/freelang.xml
/usr/lib/firefox/distribution/searchplugins/locale/br/google.xml
/usr/lib/firefox/distribution/searchplugins/locale/br/klask.xml
/usr/lib/firefox/distribution/searchplugins/locale/br/wikipedia-br.xml
/usr/lib/firefox/distribution/searchplugins/locale/br/yahoo-france.xml