/usr/share/doc/syslog-ng-mod-mongodb/changelog.Debian.gz is in syslog-ng-mod-mongodb 3.3.4.dfsg-2ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/syslog-ng-mod-mongodb/../libsyslog-ng-3.3.4/changelog.Debian.gz