Hello,

If the captchaEndpoint variable already has GET parameters (which is the case for all Wordpress website for example, ajax calls have a "?action=xxx" parameter), the endpoint gets concatenated with "?get=" here:
https://github.com/captcha-com/jquery-captcha/blob/master/src/jquery-captcha.js#L99

Because there are two "?" in the URL, it becomes invalid (returns a HTTP 400 bad request). Other queries use "$.ajax", which checks the presence of a "?" in the URL