/usr/share/doc/libcrypto++-dev/changelog.Debian.gz is in libcrypto++-dev 5.6.4-8.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libcrypto++-dev/../libcrypto++6/changelog.Debian.gz
/usr/share/doc/libcrypto++-dev/../libcrypto++6/changelog.Debian.gz