/usr/lib/firefox/ is in firefox-locale-ast 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-ast@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/ast/
/usr/lib/firefox/distribution/searchplugins/locale/ast/bing.xml
/usr/lib/firefox/distribution/searchplugins/locale/ast/diccionariu-alla.xml
/usr/lib/firefox/distribution/searchplugins/locale/ast/duckduckgo.xml
/usr/lib/firefox/distribution/searchplugins/locale/ast/eBay-es.xml
/usr/lib/firefox/distribution/searchplugins/locale/ast/google.xml
/usr/lib/firefox/distribution/searchplugins/locale/ast/wikipedia-ast.xml
/usr/lib/firefox/distribution/searchplugins/locale/ast/yahoo-es.xml