/usr/lib/firefox/ is in firefox-locale-fa 11.0+build1-0ubuntu4.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/firefox-addons/extensions/
/usr/lib/firefox-addons/extensions/langpack-fa@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/fa/
/usr/lib/firefox/distribution/searchplugins/locale/fa/amazondotcom.xml
/usr/lib/firefox/distribution/searchplugins/locale/fa/answers.xml
/usr/lib/firefox/distribution/searchplugins/locale/fa/bing.xml
/usr/lib/firefox/distribution/searchplugins/locale/fa/google.xml
/usr/lib/firefox/distribution/searchplugins/locale/fa/wikipedia-fa.xml
/usr/lib/firefox/distribution/searchplugins/locale/fa/yahoo.xml