Temp files for fping are created world readable:
[[email protected] ~]# ls -l /tmp/zabbix_*pinger
rw-rw-r- 1 zabbix zabbix 383 nov 5 09:24 /tmp/zabbix_server_5498.pinger
rw-rw-r- 1 zabbix zabbix 13 nov 5 09:24 /tmp/zabbix_server_5502.pinger
AFAIK these file contain hostnames only, but it would be better to be on the safe side and supress the read flag for others.