The April 2011 Cumulative Security Update for Internet Explorer is now available via Windows Update. This security update resolves four privately reported vulnerabilities and one publicly disclosed vulnerability in Internet Explorer. This security update is rated Critical for Internet Explorer 6, Internet Explorer 7, and Internet Explorer 8 on Windows clients; and Moderate for Internet Explorer 6, Internet Explorer 7, and Internet Explorer 8 on Windows servers. Internet Explorer 9 is not affected by the vulnerabilities.
The most severe vulnerabilities could allow remote code execution if a user views a specially crafted Web page using Internet Explorer. An attacker who successfully exploited any of these vulnerabilities could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.
The update addresses the vulnerabilities by modifying the way that Internet Explorer handles objects in memory, content during certain processes, and script during certain processes. For more information about the vulnerabilities, see the full bulletin.
The majority of customers have automatic updating enabled and will not need to take any action because this security update will be downloaded and installed automatically. Customers who have not enabled automatic updating need to check for updates and install this update manually. For information about specific configuration options in automatic updating, see Microsoft Knowledge Base Article 294871.
For administrators and enterprise installations, or end users who want to install this security update manually, Microsoft recommends that customers apply the update immediately using update management software, or by checking for updates using the Microsoft Update service.
—Tyson Storey, Lead Program Manager, Internet Explorer