/usr/lib/x86_64-linux-gnu/libgtkextra-x11-3.0.so.8 is in libgtkextra-3.0 3.3.3-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libgtkextra-x11-3.0.so.8.1.3
/usr/lib/x86_64-linux-gnu/libgtkextra-x11-3.0.so.8.1.3