A random hash is actually fine -- the problem is that they are using only 5 characters. Had the programmers decided to go with a single additional character, t

A random hash is actually fine -- the problem is that they are using only 5 characters. Had the programmers decided to go with a single additional character, this vulnerability would be much, much less severe. If they chose seven characters, it would be difficult to even grab a single random image. Ten characters, and it would take half a century per image.