/usr/lib/x86_64-linux-gnu/libmuparserx.so is in libmuparserx-dev 4.0.7+dfsg-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libmuparserx.so.4.0.7
/usr/lib/x86_64-linux-gnu/libmuparserx.so.4.0.7