ArcGIS Server contains an input validation weakness in the login redirection workflow. An Authenticated attacker could exploit this issue by sending a specially crafted request, Successful exploitation may result in the application redirecting the browser to an unintended, untrusted site, resulting in a limited confidentiality impact under specific user interaction conditions. The vulnerability affects only the client side navigation logic during authentication and remains confined to the same security boundary. No server side compromise or cross component impact is possible.  This issue affects ArcGIS Server 11.5.