/usr/lib/x86_64-linux-gnu/libxfsm-4.6.so is in xfce4-session 4.10.1-3ubuntu5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libxfsm-4.6.so.0.0.0
/usr/lib/x86_64-linux-gnu/libxfsm-4.6.so.0.0.0