CVE-2020-23992: 
Nagios XI vulnerability analysis and mitigation

A reflected cross-site scripting (XSS) vulnerability was discovered in Nagios XI version 5.7.1. The vulnerability (CVE-2020-23992) allows remote attackers to execute arbitrary code via the returnUrl parameter in a crafted GET request (GitHub POC).

The vulnerability exists in the CCM component of Nagios XI 5.7.1. An attacker can exploit this by manipulating the 'returnUrl' parameter in GET requests to '/includes/components/ccm/' endpoint. The vulnerability has been assigned a CVSS v3.1 Base Score of 6.1 MEDIUM (Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N) (NVD).

If successfully exploited, this vulnerability allows attackers to execute arbitrary code in the context of the user's browser session. This could lead to theft of sensitive information, session hijacking, or other malicious actions performed on behalf of the victim user who opens a specially crafted link or third-party web page.

Users should upgrade to a patched version of Nagios XI. Until then, administrators should implement input validation and output encoding for the returnUrl parameter, and consider using Content Security Policy (CSP) headers to help prevent XSS attacks.