/usr/lib/v_sim/plug-ins/libxsf.so is in v-sim-plugins 3.7.0-2ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/v_sim/plug-ins/libxsf.so.7.0.0
/usr/lib/v_sim/plug-ins/libxsf.so.7.0.0