/usr/share/cairo-dock/themes/Default-Panel/plug-ins/ is in cairo-dock-data 3.3.99.beta1.2.really.3.3.2-0ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/AlsaMixer/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/AlsaMixer/AlsaMixer.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Animated-icons/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Animated-icons/Animated-icons.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Calendar/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Calendar/Calendar.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Clipper/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Clipper/Clipper.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/GMenu/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/GMenu/GMenu.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Help/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Help/Help.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Indicator-Generic/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Indicator-Generic/Indicator-Generic.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Messaging-Menu/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Messaging-Menu/Messaging-Menu.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Recent-Events/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Recent-Events/Recent-Events.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Status-Notifier/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/Status-Notifier/Status-Notifier.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/clock/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/clock/clock.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/dialog-rendering/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/dialog-rendering/dialog-rendering.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/dnd2share/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/dnd2share/dnd2share.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/drop_indicator/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/drop_indicator/drop_indicator.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/icon-effect/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/icon-effect/icon-effect.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/illusion/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/illusion/illusion.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/logout/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/logout/logout.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/musicPlayer/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/musicPlayer/musicPlayer.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/netspeed/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/netspeed/netspeed.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/powermanager/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/powermanager/powermanager.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/quick-browser/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/quick-browser/quick-browser.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/rendering/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/rendering/rendering.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/shortcuts/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/shortcuts/shortcuts.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/showDesktop/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/showDesktop/showDesktop.conf
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/switcher/
/usr/share/cairo-dock/themes/Default-Panel/plug-ins/switcher/switcher.conf