/usr/ is in firefox-locale-et 28.0+build2-0ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/
/usr/lib/firefox/
/usr/lib/firefox/distribution/
/usr/lib/firefox/distribution/searchplugins/
/usr/lib/firefox/distribution/searchplugins/locale/
/usr/lib/firefox/distribution/searchplugins/locale/et/
/usr/lib/firefox/distribution/searchplugins/locale/et/eBay.xml
/usr/lib/firefox/distribution/searchplugins/locale/et/eki-ee.xml
/usr/lib/firefox/distribution/searchplugins/locale/et/google.xml
/usr/lib/firefox/distribution/searchplugins/locale/et/wikipedia-et.xml
/usr/lib/firefox/distribution/searchplugins/locale/et/duckduckgo.xml
/usr/lib/firefox/distribution/searchplugins/locale/et/osta-ee.xml
/usr/lib/firefox/distribution/searchplugins/locale/et/neti-ee.xml
/usr/lib/firefox-addons/
/usr/lib/firefox-addons/extensions/
/usr/lib/firefox-addons/extensions/langpack-et@firefox.mozilla.org.xpi
/usr/share/
/usr/share/doc/
/usr/share/doc/firefox-locale-et/
/usr/share/doc/firefox-locale-et/copyright
/usr/share/doc/firefox-locale-et/changelog.Debian.gz