/usr/share/doc/kde/HTML/en/khelpcenter/common is in khelpcenter4 4:4.8.2-0ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/kde/HTML/en/khelpcenter/../common
/usr/share/doc/kde/HTML/en/khelpcenter/../common