CAPTCHA is almost ubiquitous in today’s web applications and an extremely popular CAPTCHA implementation is Google’s, namely reCaptcha. reCaptcha provides an audio version for visually-impaired users. Researchers manage to make use of free speech-to-text services to defeat audio reCaptcha.
unCaptcha: Talk is cheap in defeating reCaptcha
Source: unCaptcha: A Low-Resource Defeat of reCaptcha’s Audio Challenge