/usr/share/cairo-dock/themes/Default-Single/launchers/ is in cairo-dock-data 3.4.1-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/cairo-dock/themes/Default-Single/launchers/01firefox.desktop
/usr/share/cairo-dock/themes/Default-Single/launchers/01gcalctool.desktop
/usr/share/cairo-dock/themes/Default-Single/launchers/01gimp.desktop
/usr/share/cairo-dock/themes/Default-Single/launchers/01gnome-terminal.desktop
/usr/share/cairo-dock/themes/Default-Single/launchers/01ooo-writer.desktop
/usr/share/cairo-dock/themes/Default-Single/launchers/01pidgin.desktop
/usr/share/cairo-dock/themes/Default-Single/launchers/01separator.desktop
/usr/share/cairo-dock/themes/Default-Single/launchers/01thunderbird.desktop
/usr/share/cairo-dock/themes/Default-Single/launchers/01ubuntu-software-center.desktop
/usr/share/cairo-dock/themes/Default-Single/launchers/02separator.desktop
/usr/share/cairo-dock/themes/Default-Single/launchers/03separator.desktop