A security feature bypass vulnerability exists when Microsoft browsers improperly handle redirect requests. The vulnerability allows Microsoft browsers to bypass CORS redirect restrictions, and to follow redirect requests that should otherwise be ignored. An attacker who successfully exploited the vulnerability could force the browser to send data that would otherwise be restricted to a destination website of the attacker's choice.
In a web-based attack scenario, an attacker could host a specially crafted website that is designed to exploit the vulnerability through Microsoft browsers and then convince a user to view the website. The attacker could also take advantage of compromised websites, and websites that accept or host user-provided content or advertisements. These websites could contain specially crafted content that could exploit the vulnerability.
The security update addresses the vulnerability by modifying how affected Microsoft browsers handle redirect requests.