While setting up Mantis, something went wrong, and dbconfig-common did not manage to create a database for Mantis (maybe user error). So I used dpkg-reconfigure:
$ sudo dpkg-reconfigure mantis
And after that, having a working Mantis install, I noticed the world readable config file.
My steps were:
$ sudo apt-get install mantis
While setting up Mantis, something went wrong, and dbconfig-common did not manage to create a database for Mantis (maybe user error). So I used dpkg-reconfigure:
$ sudo dpkg-reconfigure mantis
And after that, having a working Mantis install, I noticed the world readable config file.