/usr/lib/mono/4.5/xsp4.exe is in mono-xsp4 4.2-2.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/mono/4.5/../gac/xsp4/4.2.0.0__0738eb9f132ed756/xsp4.exe
/usr/lib/mono/4.5/../gac/xsp4/4.2.0.0__0738eb9f132ed756/xsp4.exe