Add an extra space at the end of the captcha response.

4chan_x.user.js

@@ -1856,7 +1856,7 @@
         mode: 'regist',
         pwd: (m = d.cookie.match(/4chan_pass=([^;]+)/)) ? decodeURIComponent(m[1]) : $('[name=pwd]').value,
         recaptcha_challenge_field: challenge,
-        recaptcha_response_field: response
+        recaptcha_response_field: response + ' '
       };
       qr.status({
         progress: '...'

script.coffee

@@ -1490,7 +1490,7 @@ qr =
       mode:    'regist'
       pwd: if m = d.cookie.match(/4chan_pass=([^;]+)/) then decodeURIComponent m[1] else $('[name=pwd]').value
       recaptcha_challenge_field: challenge
-      recaptcha_response_field:  response
+      recaptcha_response_field:  response + ' '
 
     # Starting to upload might take some time.
     # Provide some feedback that we're starting to submit.