A vulnerability in the user management functions of Cisco Registered Envelope Service could allow an unauthenticated, remote attacker to discover sensitive user information. The attacker could use this information to conduct additional reconnaissance attacks. The vulnerability is due to an insecure configuration that allows improper indexing. An attacker could exploit this vulnerability by using a search engine to look for specific data strings. A successful exploit could allow the attacker to discover certain sensitive information about the application, including usernames.