/usr/lib/x86_64-linux-gnu/libvtkGUISupportQtWebkit-6.3.so is in libvtk6-qt-dev 6.3.0+dfsg1-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libvtkGUISupportQtWebkit-6.3.so.6.3