/usr/share/doc/gthumb-dev/changelog.Debian.gz is in gthumb-dev 3:3.4.3-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/gthumb-dev/../gthumb/changelog.Debian.gz
/usr/share/doc/gthumb-dev/../gthumb/changelog.Debian.gz