sexy captcha can be hacked by a js

http://blog.lukeblackamore.com/2009/10/sexy-captcha-new-drag-and-drop-ca...

some one indicated:
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it can be sexy, and whatever, but it just wont stop anybody, who want to avoid this captcha.
here is the solver:

var res=document.querySelector(".targetWrapper .target").style["background-position"].match(/\d+/);
[].map.call(document.querySelectorAll(".draggable"),function(a){
if(a.style["background-position"].match(/\d+/)[0]==res){
return document.querySelector(".captchaAnswer").value=a.id
}
});

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I tested, this bug is true, please provide some idea if you happened to visit here.