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so-called buffer overflow vulnerability, which an attacker can exploit by sending more input to a program than the application expects, could allow the owner of a Web site to run code on the person's computer. Buffer overflows are an old type of vulnerability that still crop up frequently in programs. The flaw occurs in a component of Internet Explorer that delivers Web addresses to the browser from other sources--for instance, if a person clicked on a URL in an e-mail or a Word document.