juct writes: "In March 2006 Apple defused a security problem in Apple Mail that made it possible to inject disguised malignant code. In Leopard, the patch was apparently forgotten. This means that you can inadvertently start an executable by double-clicking a mail attachment that looks like a JPEG image file. This works with special attachmnets of the MIME type AppleDouble, that carry information which application should be used to open a file. In Tiger you got a warning about a program being opened, Leopard silently executes a shell script with Terminal.app. heise Security provides a demo, where you can check for yourself."