status.cgi in Nagios 4.0 before 4.0 beta4 and 3.x before 3.5.1 does not properly restrict access to certain users that are a contact for a service, which allows remote authenticated users to obtain sensitive information about hostnames via the servicegroup (1) overview, (2) summary, or (3) grid style in status.cgi.  NOTE: this behavior is by design in most 3.x versions, but the upstream vendor "decided to change it for Nagios 4" and 3.5.1.