/usr/lib/libITKEXPAT.so is in libinsighttoolkit3-dev 3.20.1+git20120521-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/libITKEXPAT.so.3.20
/usr/lib/libITKEXPAT.so.3.20