[stryderunknown]

I haven't installed the addon, however that's because I'm in the process of look at writing one myself. However I do see a slight flaw in how your addon works (without getting into the reverse engineering of how it works).

The problem is 'finite possibilities', if a Bot were to choose to click(well... emulate a click) the first image every time eventually it would get the right image because of the randomisation process.

It could be beneficial to log the number of attempts (I'd guess in the db session table) and perhaps blacklist those that reach a certain threshold. Some might suggest generating random numbers for your show.php?# , however again a bot would be able to read it.

One way would to be add the addition of say 4-binary digits via the GD library to the bottom of each image, the user can then be asked to type the binary reference as well as click an image. (And the reference doesn't have to be from the same image as they click).

This increases the complexity and lessens the chances that both will fall on the first image (in fact you could alter the randomisation method to not allow them to fall on the same image)

I would hack that version myself, however I've got another one up my sleeve

Other than that keep up the good work (as well as all those that aid people coding/designing)