/usr/share/xfce4/ is in xfce4-panel 4.12.0-3ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/share/xfce4/panel/
/usr/share/xfce4/panel/plugins/
/usr/share/xfce4/panel/plugins/actions.desktop
/usr/share/xfce4/panel/plugins/applicationsmenu.desktop
/usr/share/xfce4/panel/plugins/clock.desktop
/usr/share/xfce4/panel/plugins/directorymenu.desktop
/usr/share/xfce4/panel/plugins/launcher.desktop
/usr/share/xfce4/panel/plugins/pager.desktop
/usr/share/xfce4/panel/plugins/separator.desktop
/usr/share/xfce4/panel/plugins/showdesktop.desktop
/usr/share/xfce4/panel/plugins/systray.desktop
/usr/share/xfce4/panel/plugins/tasklist.desktop
/usr/share/xfce4/panel/plugins/windowmenu.desktop