/usr/share/doc/libxmlsec1-dev/TODO.Debian is in libxmlsec1-dev 1.2.20-2ubuntu4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libxmlsec1-dev/../libxmlsec1/TODO.Debian
/usr/share/doc/libxmlsec1-dev/../libxmlsec1/TODO.Debian