It now plans to issue four security bulletins on Tuesday, rather than the eight originally announced, the software giant said Friday in an updated notice on its Web site.
Three bulletins will contain fixes for Office, at least one of which will be rated "critical," Microsoft said. Critical vulnerabilities typically can allow a worm to spread or allow a Windows system to be fully compromised with minor or no interaction from the person using it. The fourth bulletin, for Windows, is also tagged critical.
On Thursday, Microsoft listed eight bulletins it intended to issue next week in its monthly patch cycle. It appears to have pulled two bulletins for Windows, one for Windows and Visual Studio and one for Windows and Office. These patches will now likely be released on a future Patch Tuesday.
The Redmond, Wash.-based software giant did not provide any explanation for pulling the bulletins only a few days before their scheduled release. "There are many factors that impact the release of a security update, and every vulnerability presents its own unique challenges," a Microsoft representative said in an e-mailed statement.
The company does not specify ahead of time which security vulnerabilities are addressed by its patches. As a result, it's unknown what security holes will now be left without a fix. eEye Digital Security, on its Zero-Day Tracker Web site, lists eight zero-day vulnerabilities that Microsoft still has to address, with four each in Office and Windows.
Zero-day vulnerabilities are security holes that have been publicly disclosed without a fix being available. In some cases, exploit code may be available for such a flaw, and there may be cyberattacks that take advantage of it. However, Microsoft's patches often address vulnerabilities that have not been publicly disclosed.
The company sometimes deviates from the Patch Tuesday advance notification. Last month, for example, it issued one more security bulletin than it had said it would. It has also dropped bulletins, citing quality issues. However, it has never before pulled four bulletins.
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