A vulnerability in the web-based guest portal of Cisco Identity Services Engine (ISE) could allow an authenticated, remote attacker to conduct a cross-site scripting (XSS) attack against a user of the web-based management interface. The vulnerability is due to insufficient validation of user-supplied input that is processed by the web-based interface. An attacker could exploit this vulnerability by persuading a user of the interface to click a crafted link. A successful exploit could allow the attacker to execute arbitrary script code in the context of the interface or access sensitive browser-based information. Cisco ISE software version 2.1 is affected.