Microsoft has issued a software patch for what it calls a critical security flaw in its Windows Millennium Edition operating system, according to the company's Web site.

The security flaw is a "buffer run" vulnerability, which, if exploited, lets an attacker execute software programs on a victim's computer. The flaw could allow attackers to delete files, run software code and modify programs that appear to have originated locally on the victim's PC, according to the warning on Microsoft's Web site.