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