/usr/lib/freeradius/rlm_fastusers.so is in freeradius 2.2.8+dfsg-0.1build2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/freeradius/rlm_fastusers-2.2.8.so
/usr/lib/freeradius/rlm_fastusers-2.2.8.so