/usr/lib/x86_64-linux-gnu/libxfce4panel-1.0.so is in xfce4-panel-dev 4.12.2-1ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libxfce4panel-1.0.so.4.0.0
/usr/lib/x86_64-linux-gnu/libxfce4panel-1.0.so.4.0.0