/usr/share/doc/libctpp2-dev/TODO is in libctpp2-dev 2.8.3-23.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libctpp2-dev/../libctpp2-2v5/TODO
/usr/share/doc/libctpp2-dev/../libctpp2-2v5/TODO