/usr/lib/ is in firefox-locale-bs 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/bs/
/usr/lib/firefox/distribution/searchplugins/locale/bs/eBay.xml
/usr/lib/firefox/distribution/searchplugins/locale/bs/google.xml
/usr/lib/firefox/distribution/searchplugins/locale/bs/twitter.xml
/usr/lib/firefox/distribution/searchplugins/locale/bs/duckduckgo.xml
/usr/lib/firefox/distribution/searchplugins/locale/bs/pik.xml
/usr/lib/firefox/distribution/searchplugins/locale/bs/wikipedia-bs.xml
/usr/lib/firefox/distribution/searchplugins/locale/bs/yahoo.xml
/usr/lib/firefox/distribution/searchplugins/locale/bs/tajpi.xml
/usr/lib/firefox-addons/
/usr/lib/firefox-addons/extensions/
/usr/lib/firefox-addons/extensions/langpack-bs@firefox.mozilla.org.xpi