Microsoft will issue a security update on Tuesday that patches a total of seven vulnerabilities in Windows and related applications.

One of the vulnerabilities affects Windows Media Player and is rated 'critical'. This is Microsoft's highest severity rating and typically means that a system can become compromised without user interaction.

Windows itself is scheduled to receive four security patches, at least one of which is rated 'critical'.

Microsoft is also preparing an 'important' update for a flaw that affects both Windows and the Office productivity suite, and the final fix is for Office and is rated 'important'.

The company did not say whether the upcoming patch will also include a fix for a critical vulnerability affecting Internet Explorer 5 and 5.5, about which it sent out a security advisory on Wednesday. 

Microsoft typically publishes its security updates on the second Tuesday of the month and gives notice about the kind of updates that it is preparing in the week prior to the release. This schedule is aimed at helping administrators to prepare.

The company publishes out-of-cycle updates on rare occasions. Last month Microsoft was forced to rush out a fix for a vulnerability in the WMF graphics format that attackers were actively exploiting.