/usr/share/ is in xul-ext-ubufox 2.8-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/xul-ext/
/usr/share/xul-ext/ubufox/
/usr/share/xul-ext/ubufox/chrome.manifest
/usr/share/xul-ext/ubufox/defaults/
/usr/share/xul-ext/ubufox/defaults/preferences/
/usr/share/xul-ext/ubufox/defaults/preferences/ubufox.js
/usr/share/xul-ext/ubufox/defaults/preferences/ubuntu-mods.js
/usr/share/xul-ext/ubufox/scripts/
/usr/share/xul-ext/ubufox/scripts/check-component-enabled.py
/usr/share/xul-ext/ubufox/chrome/
/usr/share/xul-ext/ubufox/chrome/ubufox.jar
/usr/share/xul-ext/ubufox/install.rdf
/usr/share/xul-ext/ubufox/components/
/usr/share/xul-ext/ubufox/components/AboutStartpage.js
/usr/share/xul-ext/ubufox/components/UpdateNotifier.js
/usr/share/doc/
/usr/share/doc/xul-ext-ubufox/
/usr/share/doc/xul-ext-ubufox/example-homepage.properties
/usr/share/doc/xul-ext-ubufox/copyright
/usr/share/doc/xul-ext-ubufox/changelog.Debian.gz
/usr/share/mozilla/
/usr/share/mozilla/extensions/
/usr/share/mozilla/extensions/{ec8030f7-c20a-464f-9b0e-13a3a9e97384}/
/usr/share/xul-ext/ubufox/defaults/preferences/000system.js
/usr/share/mozilla/extensions/{ec8030f7-c20a-464f-9b0e-13a3a9e97384}/ubufox@ubuntu.com