/usr/lib/x86_64-linux-gnu/libnjb.so is in libnjb-dev 2.2.7~dfsg0-4+b2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libnjb.so.5.1.1
/usr/lib/x86_64-linux-gnu/libnjb.so.5.1.1