/usr/lib/firefox/ is in firefox-locale-sv 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-sv-SE@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/sv-SE/
/usr/lib/firefox/distribution/searchplugins/locale/sv-SE/allaannonser-sv-SE.xml
/usr/lib/firefox/distribution/searchplugins/locale/sv-SE/bing.xml
/usr/lib/firefox/distribution/searchplugins/locale/sv-SE/duckduckgo.xml
/usr/lib/firefox/distribution/searchplugins/locale/sv-SE/google.xml
/usr/lib/firefox/distribution/searchplugins/locale/sv-SE/prisjakt-sv-SE.xml
/usr/lib/firefox/distribution/searchplugins/locale/sv-SE/tyda-sv-SE.xml
/usr/lib/firefox/distribution/searchplugins/locale/sv-SE/wikipedia-sv-SE.xml
/usr/lib/firefox/distribution/searchplugins/locale/sv-SE/yahoo-sv-SE.xml