Microsoft explained why the flaw went unfixed. "We provide security updates for beta versions of Windows through Windows Update for Critical issues only," said , a spokesman for the (MSRC), in a Tuesday. "So the vulnerability will be addressed in the next public release for Windows 7."

Of the three bugs patched by the MS09-001 security update today, just one is pertinent to Windows 7, Budd added. That vulnerability, designated as CVE-2008-4114, is a denial-of-service bug rated "moderate," the second step in Microsoft's four-level scoring system.

The remaining two vulnerabilities -- both labeled "critical" by Microsoft -- affect Windows 2000, XP and Server 2003; one of them also affects Windows Vista and Server 2008.

Windows 7 beta, which was , will be available for download .