/usr/share/ is in xubuntu-default-settings 16.04.6.
This file is owned by root:root, with mode 0o755.
..
/usr/share/gconf/
/usr/share/gconf/defaults/
/usr/share/gconf/defaults/20_xubuntu-default-settings
/usr/share/xubuntu/
/usr/share/xubuntu/applications/
/usr/share/xubuntu/applications/debian-xterm.desktop
/usr/share/xubuntu/applications/debian-uxterm.desktop
/usr/share/xubuntu/applications/Thunar-bulk-rename.desktop
/usr/share/xubuntu/applications/defaults.list
/usr/share/xubuntu/applications/xfhelp4.desktop
/usr/share/xubuntu/applications/thunar-settings.desktop
/usr/share/xubuntu/applications/Thunar.desktop
/usr/share/xubuntu/applications/xfce4-terminal.desktop
/usr/share/polkit-1/
/usr/share/polkit-1/actions/
/usr/share/polkit-1/actions/com.ubuntu.pkexec.mousepad.policy
/usr/share/xsessions/
/usr/share/xsessions/xubuntu.desktop
/usr/share/lightdm/
/usr/share/lightdm/lightdm-gtk-greeter.conf.d/
/usr/share/lightdm/lightdm-gtk-greeter.conf.d/30_xubuntu.conf
/usr/share/lightdm/lightdm.conf.d/
/usr/share/lightdm/lightdm.conf.d/60-xubuntu.conf
/usr/share/doc/
/usr/share/doc/xubuntu-default-settings/
/usr/share/doc/xubuntu-default-settings/changelog.gz
/usr/share/doc/xubuntu-default-settings/copyright
/usr/share/glib-2.0/
/usr/share/glib-2.0/schemas/
/usr/share/glib-2.0/schemas/20_xubuntu-default-settings.gschema.override