/usr/share/nagios3/ is in nagios3-common 3.5.1-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/nagios3/debian/
/usr/share/nagios3/plugins/
/usr/share/nagios3/plugins/eventhandlers/
/usr/share/nagios3/plugins/eventhandlers/disable_active_service_checks
/usr/share/nagios3/plugins/eventhandlers/disable_notifications
/usr/share/nagios3/plugins/eventhandlers/distributed-monitoring/
/usr/share/nagios3/plugins/eventhandlers/distributed-monitoring/obsessive_svc_handler
/usr/share/nagios3/plugins/eventhandlers/distributed-monitoring/submit_check_result_via_nsca
/usr/share/nagios3/plugins/eventhandlers/enable_active_service_checks
/usr/share/nagios3/plugins/eventhandlers/enable_notifications
/usr/share/nagios3/plugins/eventhandlers/redundancy-scenario1/
/usr/share/nagios3/plugins/eventhandlers/redundancy-scenario1/handle-master-host-event
/usr/share/nagios3/plugins/eventhandlers/redundancy-scenario1/handle-master-proc-event
/usr/share/nagios3/plugins/eventhandlers/submit_check_result