MS09-009  Vulnerabilities in Microsoft Office Excel Could Cause Remote Code Execution (968557)

Critical - Remote Code Execution This security update resolves a privately reported vulnerability and a publicly disclosed vulnerability in Microsoft Office Excel. The vulnerabilities could allow remote code execution if the user opens a specially crafted Excel file. An attacker who successfully exploited 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. 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.
Bulletin details at Microsoft.com