As we all know, CAPTCHAs exist to prevent machines from brute-forcing passwords or spamming comments with advertisements. Typically, a CAPTCHA consists of 4 digits with some interference lines to thwart brute-force attacks as much as possible. The problem is... there's also a kind of absurd CAPTCHA in this world. Image source: http://imbushuo.net/archives/58 . I just want to say: What's the point of this CAPTCHA? Any random program could extract and auto-fill it. According to imbushuo: What』s more, the verification process is completed in the client side… ( later I found that I could bypass the CAPTCHA by sending the HTTP request directly. ) He actually wrote a program that logged in successfully without even sending back the CAPTCHA! This CAPTCHA is truly "impressive....