/usr/lib/x86_64-linux-gnu/libdbusmenu-gtk3.so.4 is in libdbusmenu-gtk3-4 12.10.3+16.04.20160223.1-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libdbusmenu-gtk3.so.4.0.12