/usr/share/doc/libmpfr4-dbg/changelog.gz is in libmpfr4-dbg 3.1.5-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libmpfr4-dbg/../libmpfr4/changelog.gz
/usr/share/doc/libmpfr4-dbg/../libmpfr4/changelog.gz