Many Intruders Remain Unpredictable

The second of the three security principles listed in my first book is:

Many intruders are unpredictable.

I think the new Adobe Acrobat Reader vulnerability demonstrates this perfectly. (I'm not calling Stefano Di Paola an intruder; anyone who uses his technique maliciously is an intruder, though.)

Who would have thought to abuse a .pdf viewer in such a manner? Read more about the problem here.

This event reminds me of soccer goal security.