An elevation of privilege vulnerability exists when Microsoft IIS Server fails to properly sanitize a specially crafted request. An attacker who successfully exploited this vulnerability could then perform cross-site scripting attacks on affected systems and run script in the security context of the current user. These attacks could allow the attacker to read content that the attacker is not authorized to read, use the victim's identity to take actions on behalf of the victim, and inject malicious content in the victim’s browser.
For this vulnerability to be exploited, a user must click a specially crafted URL.
In an email attack scenario, an attacker could exploit the vulnerability by sending an email message containing the specially crafted URL to the user and by convincing the user to click on the specially crafted URL.
In a web-based attack scenario, an attacker would have to host a website that contains a specially crafted URL. In addition, compromised websites and websites that accept or host user-provided content could contain specially crafted content that could exploit this vulnerability. An attacker would have no way to force users to visit a specially crafted website. Instead, an attacker would have to convince users to visit the website, typically by getting them to click a link in an email or instant message that directs them to the affected website by way of a specially crafted URL.
The security update addresses the vulnerability by correcting how Microsoft IIS Server sanitizes web requests.