/usr/lib/x86_64-linux-gnu/libMagPlus.so.3 is in libmagplus3 2.18.15-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libMagPlus.so.3.0.0
/usr/lib/x86_64-linux-gnu/libMagPlus.so.3.0.0