/usr/lib/firefox/ is in firefox-locale-as 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-as@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/as/
/usr/lib/firefox/distribution/searchplugins/locale/as/amazondotcom.xml
/usr/lib/firefox/distribution/searchplugins/locale/as/creativecommons.xml
/usr/lib/firefox/distribution/searchplugins/locale/as/duckduckgo.xml
/usr/lib/firefox/distribution/searchplugins/locale/as/eBay-in.xml
/usr/lib/firefox/distribution/searchplugins/locale/as/google.xml
/usr/lib/firefox/distribution/searchplugins/locale/as/wikipedia-as.xml
/usr/lib/firefox/distribution/searchplugins/locale/as/yahoo-in.xml