Severity Rating: Critical - Revision Note: Bulletin published.Summary: This security update resolves several privately reported vulnerabilities that could allow remote code execution if a user opens a specially crafted Excel file that includes a malformed record object. An attacker who successfully exploited any of these vulnerabilities could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

Read more at: http://www.microsoft.com/technet/security/bulletin/MS09-021.mspx?pubDate=2009-06-09