From GGUS ticket:

The service needs to restrict further what can be seen with any IGTF
certificate: only the list of certificate subject DNs for a given VOMS group or
role shall be exposed to any authenticated user, because that functionality is
needed for constructing grid-mapfiles. Users should still be able to access
their own entry, while only the admins of a given VO shall be able to see the
details of other users in that VO.