Corsaire Security Advisory – By using MIME encapsulation techniques centered on both standard and non-standard Content-Transfer-Encoding mechanisms, embedded file attachment blocking functionality can be evaded.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/34357/c030804-005.txt
Source: https://packetstormsecurity.com/files/34357/Corsaire-Security-Advisory-2003-08-04.5.html