Microsoft on Thursday said it plans to issue three Security Bulletins next Tuesday, March 10, one of which is designated "critical" and the other two of which are designated "important."

Conspicuously absent is a fix for the Excel security flaw that Microsoft warned about just over a week ago.

Microsoft provided very little information about the patches it will issue other than stating that the flaws affect Windows. The "critical" vulnerability allows remote code execution, while the two "important" vulnerabilities allow spoofing.

The affected versions of Windows include Windows Vista, Windows XP, Windows Server 2008, Windows Server 2003, and Windows Server 2000.

Microsoft typically issues its patches around 10 a.m. Pacific time on the second Tuesday of the month, a day often referred to by Windows IT administrators as "Patch Tuesday." On the following day, the company plans to host a Webcast at 11 a.m. Pacific time to answer customer questions about the bulletins.

It was Symantec researchers in Japan who first detected the malware being embedded in Microsoft Office Excel 2007 spreadsheets, according to Symantec researcher Patrick Fitzgerald.

After analyzing the files, the researchers found that the malware authors were exploiting a vulnerability in Excel that allowed them to execute malicious files on the victim's system. The vulnerability affects files that use the old .xls binary format but not the newer .xlsx format.

Microsoft said it expects to release a fix for the Excel vulnerability once the patch has been tested. It notes that the vulnerability cannot be exploited automatically through e-mail. The victim has to first open the infected Excel file.

Take part in InformationWeek's fourth annual NAC enterprise security strategy survey before March 5 and be eligible to win an iPod Touch. Find out more.