Actually, the captcha predicate is a GET request that looks like this: http://en.lichess.org/captcha/78pkfjgz?solution=e5+e4 http://en.lichess.org/captcha/78pk

Actually, the captcha predicate is a GET request that looks like this: http://en.lichess.org/captcha/78pkfjgz?solution=e5+e4 http://en.lichess.org/captcha/78pkfjgz?solution=e5+e4 which returns 1 or 0. So the brute force captcha solution is to go through 8^4 (~4k) get requests, which you could code in five minutes and execute in a minute.