Microsoft is preparing to release eight Windows security patches on Tuesday as part of its monthly patch release cycle, the company said in a security bulletin on its website. 

At least one of the fixes affects a flaw which the software vendor rates as 'critical', its highest severity rating. Microsoft did not provide additional information about the expected patches.

Tuesday will also see the release of one patch for Microsoft Exchange which is rated 'important'.

Microsoft has opted for a monthly patch release cycle to allow system administrators to prepare for upcoming fixes.

The patch release traditionally coincides with an update of Microsoft's Malicious Software Removal Tool and is followed by a webcast. This month's webcast is on Wednesday at 11am US Pacific Time (7pm BST). 

Last month Microsoft promised a single security fix for Windows rated as 'critical', but pulled the release at the last moment over quality concerns.

The security bulletin did not say whether this fix will be included in October's patches.