/usr/lib/firefox/ is in firefox-locale-ko 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-ko@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/ko/
/usr/lib/firefox/distribution/searchplugins/locale/ko/danawa-kr.xml
/usr/lib/firefox/distribution/searchplugins/locale/ko/daum-kr.xml
/usr/lib/firefox/distribution/searchplugins/locale/ko/duckduckgo.xml
/usr/lib/firefox/distribution/searchplugins/locale/ko/google.xml
/usr/lib/firefox/distribution/searchplugins/locale/ko/naver-kr.xml
/usr/lib/firefox/distribution/searchplugins/locale/ko/wikipedia-kr.xml