/usr/lib/x86_64-linux-gnu/libdbusmenu-jsonloader.so is in libdbusmenu-jsonloader-dev 16.04.1+18.04.20171206-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libdbusmenu-jsonloader.so.4.0.12