Clicking on a link or visiting a web page could allow someone complete control over your computer, unless you're not running as an administrator, which you are.

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Microsoft Security Bulletin MS08-024 - Critical

Executive Summary

This security update resolves one privately reported vulnerability. The vulnerability could allow remote code execution if a user viewed a specially crafted Web page using Internet Explorer. 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 security update is rated Critical for all supported releases of Internet Explorer. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The update removes the vulnerability by modifying the way that Internet Explorer processes data streams. For more information about the vulnerability, see the Frequently Asked Questions (FAQ) subsection under the next section, Vulnerability Information.

Recommendation. Microsoft recommends that customers apply the update immediately.