Nagios Log Server 2.1.3 allows XSS by visiting /profile and entering a crafted name field that is mishandled on the /admin/users page. Any malicious user with limited access can store an XSS payload in his Name. When any admin views this, the XSS is triggered.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.