/usr/lib/firefox/distribution/ is in firefox-locale-ku 28.0+build2-0ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/firefox/distribution/searchplugins/
/usr/lib/firefox/distribution/searchplugins/locale/
/usr/lib/firefox/distribution/searchplugins/locale/ku/
/usr/lib/firefox/distribution/searchplugins/locale/ku/amazondotcom.xml
/usr/lib/firefox/distribution/searchplugins/locale/ku/answers.xml
/usr/lib/firefox/distribution/searchplugins/locale/ku/creativecommons.xml
/usr/lib/firefox/distribution/searchplugins/locale/ku/duckduckgo.xml
/usr/lib/firefox/distribution/searchplugins/locale/ku/eBay.xml
/usr/lib/firefox/distribution/searchplugins/locale/ku/google-ku.xml
/usr/lib/firefox/distribution/searchplugins/locale/ku/wikipedia-ku.xml
/usr/lib/firefox/distribution/searchplugins/locale/ku/yahoo.xml