/usr/lib/x86_64-linux-gnu/caca/libx11_plugin.so is in libcaca0 0.99.beta19-2ubuntu0.16.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/caca/libx11_plugin.so.0.0.0
/usr/lib/x86_64-linux-gnu/caca/libx11_plugin.so.0.0.0