In its security bulletin summary for August 2007 Microsoft has published six updates for new critical vulnerabilities in its operating systems / applications as well as three important.

Critical is Microsoft’s highest vulnerability rating.

A summary describing briefly the vulnerabilities is available from Microsoft’s Security Bulletin Summary for August 2007.
From this page you will also find links to more detailed information in Microsoft's Security Bulletins MS07-042 - MS07-050.

The six critical updates address the following issues:

• One reported vulnerability in Microsoft XML Core Services.
• One reported vulnerability in OLE Automation.
• One reported vulnerability in Microsoft Excel.
• Three reported vulnerabilities Internet Explorer.
• One reported vulnerability in GDI (Graphics Rendering Engine).
• One reported vulnerability in VML (Vector Markup Language).

Updates that fixes the vulnerabilities are available from Windows automatic update mechanism for systems that support this. Alternatively, one may download updates from http://windowsupdate.microsoft.com.  

Norman advices all affected users to download the security updates as soon as possible, to be protected from potential exploits.