/usr/lib/firefox/distribution/ is in firefox-locale-zh-hans 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/zh-CN/
/usr/lib/firefox/distribution/searchplugins/locale/zh-CN/amazondotcn.xml
/usr/lib/firefox/distribution/searchplugins/locale/zh-CN/baidu.xml
/usr/lib/firefox/distribution/searchplugins/locale/zh-CN/baiduzhidao.xml
/usr/lib/firefox/distribution/searchplugins/locale/zh-CN/bing.xml
/usr/lib/firefox/distribution/searchplugins/locale/zh-CN/creativecommons.xml
/usr/lib/firefox/distribution/searchplugins/locale/zh-CN/duckduckgo.xml
/usr/lib/firefox/distribution/searchplugins/locale/zh-CN/eachnet.xml
/usr/lib/firefox/distribution/searchplugins/locale/zh-CN/google.xml
/usr/lib/firefox/distribution/searchplugins/locale/zh-CN/paipai.xml
/usr/lib/firefox/distribution/searchplugins/locale/zh-CN/wikipedia-zh-CN.xml