/usr/lib/firefox/ is in firefox-locale-an 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-an@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/an/
/usr/lib/firefox/distribution/searchplugins/locale/an/bing.xml
/usr/lib/firefox/distribution/searchplugins/locale/an/duckduckgo.xml
/usr/lib/firefox/distribution/searchplugins/locale/an/eBay-es.xml
/usr/lib/firefox/distribution/searchplugins/locale/an/google.xml
/usr/lib/firefox/distribution/searchplugins/locale/an/twitter.xml
/usr/lib/firefox/distribution/searchplugins/locale/an/wikipedia-an.xml
/usr/lib/firefox/distribution/searchplugins/locale/an/yahoo-es.xml