An information disclosure vulnerability exists when Windows Remote Assistance incorrectly processes XML External Entities (XXE). An attacker who successfully exploited the vulnerability could obtain information to further compromise the user’s system.
To exploit this condition, an attacker would need to send a specially crafted Remote Assistance invitation file to a user. A attacker could then steal text files from known locations on the victim's machine, under the context of the user, or alternatively, steal text information from URLs accessible to the victim. The stolen information could be submitted as part of the URL in HTTP request(s) to the attacker. In all cases an attacker would have no way to force a user to view the attacker-controlled content. Instead, an attacker would have to convince a user to take action.
Note that the information disclosure vulnerability by itself would not be sufficient for an attacker to compromise a system. However, an attacker could combine this vulnerability with additional vulnerabilities to further exploit the system.
The update addresses the vulnerability by correcting how Windows Remote Assistance processes XML External Entities (XXE).