A security feature bypass vulnerability exists in Internet Explorer that allows for bypassing Mixed Content warnings. This could allow for the loading of unsecure content (HTTP) from secure locations (HTTPS).
In a web-based attack scenario, an attacker could host a malicious website that is designed to exploit the security feature bypass. Alternatively, in an email or instant message attack scenario, the attacker could send the targeted user a specially crafted .url file that is designed to exploit the bypass. Additionally, compromised websites or websites that accept or host user-provided content could contain specially crafted content to exploit the security feature bypass. However, in all cases an attacker would have no way to force a user to view attacker-controlled content. Instead, an attacker would have to convince a user to take action. For example, an attacker could entice a user to either click a link that directs the user to the attacker's site or send a malicious attachment.
The security update addresses the security feature bypass by correcting how Internet Explorer handles mixed content.