Microsoft has released a critical security bulletin MS08-057. This security bulletin affects both Office 2004 and 2008. Microsoft recommends that customers apply the update immediately.
This update includes fixes for vulnerabilities that an attacker can use to overwrite the contents of a computer’s memory by using malicious code.
This security update resolves three privately reported vulnerabilities in Microsoft Office Excel that could allow remote code execution if a 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.