/usr/lib/firefox/distribution/searchplugins/ is in firefox-locale-hr 28.0+build2-0ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/firefox/distribution/searchplugins/locale/
/usr/lib/firefox/distribution/searchplugins/locale/hr/
/usr/lib/firefox/distribution/searchplugins/locale/hr/amazon-en-GB.xml
/usr/lib/firefox/distribution/searchplugins/locale/hr/bing.xml
/usr/lib/firefox/distribution/searchplugins/locale/hr/duckduckgo.xml
/usr/lib/firefox/distribution/searchplugins/locale/hr/eBay-en-GB.xml
/usr/lib/firefox/distribution/searchplugins/locale/hr/eudict.xml
/usr/lib/firefox/distribution/searchplugins/locale/hr/google.xml
/usr/lib/firefox/distribution/searchplugins/locale/hr/twitter.xml
/usr/lib/firefox/distribution/searchplugins/locale/hr/wikipedia-hr.xml
/usr/lib/firefox/distribution/searchplugins/locale/hr/yahoo.xml