/usr/share/cairo-dock/themes/Default-Panel/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-Panel/launchers/01container.desktop
/usr/share/cairo-dock/themes/Default-Panel/launchers/01firefox.desktop
/usr/share/cairo-dock/themes/Default-Panel/launchers/01gcalctool.desktop
/usr/share/cairo-dock/themes/Default-Panel/launchers/01libreoffice-calc.desktop
/usr/share/cairo-dock/themes/Default-Panel/launchers/01libreoffice-impress.desktop
/usr/share/cairo-dock/themes/Default-Panel/launchers/01libreoffice-writer.desktop
/usr/share/cairo-dock/themes/Default-Panel/launchers/01pidgin.desktop
/usr/share/cairo-dock/themes/Default-Panel/launchers/01separator.desktop
/usr/share/cairo-dock/themes/Default-Panel/launchers/01thunderbird.desktop
/usr/share/cairo-dock/themes/Default-Panel/launchers/01ubuntu-software-center.desktop
/usr/share/cairo-dock/themes/Default-Panel/launchers/02separator.desktop
/usr/share/cairo-dock/themes/Default-Panel/launchers/03separator.desktop
/usr/share/cairo-dock/themes/Default-Panel/launchers/04separator.desktop