Hi, the images installed by nagios-core under /usr/share/nagios/htdocs/images/ and /usr/share/nagios/htdocs/images/logos should be streamlined. Many images are executable and they are owned to root or nagios in a random manner. IMO all the images should just be root:root 0644
Upstream at, http://tracker.nagios.org/view.php?id=651 I plan on fixing it with a bump to nagios-4.x soon.
This should be fixed in the 4.x series just committed.