Microsoft Outlook Express 6 contains a new security feature which prevents users from opening potentially harmful file attachments. File extensions filtered by this feature are those which generally can be used to carry a virus payload.

When the file attachment security feature is turned on, any file
attachment type which could potentially carry a virus is unavailable to the recipient to either open or save.

A vulnerability exists which allows a file embedded within an HTML frame in an email message to bypass the dangerous file attachment type security feature. When a message containing an attachment embedded in this way is opened or previewed, the user is automatically prompted to open or save the attachment.

If the user attempts to open the file immediately, the action will fail. However, an assembler coded .exe attachment which has had it's extension changed to .bat will execute immediately.
Regardless of the extension type, the user is able to save the attachment to disk.

Al momento non sono state rilasciate patches al rigurardo.