/usr/share/doc/libfltk1.3-dev/CREDITS is in libfltk1.3-dev 1.3.3-7.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libfltk1.3-dev/../libfltk-cairo1.3/CREDITS
/usr/share/doc/libfltk1.3-dev/../libfltk-cairo1.3/CREDITS