Security experts from Columbia University have discovered vulnerabilities in the reCaptcha systems of Google and Facebook. They devised an attack technique that allows them to automatically influence risk analysis and bypass the protection system. The technique could be used to launch large-scale attacks. The researchers tested their attack method in offline mode, the attack method obtained a 41.57 percent success rate at 20.9 seconds per challenge. They also evaluated efficiency of their method against the Facebooks image captchas, and the results were very good.”]
Source: https://securityaffairs.co/wordpress/46186/breaking-news/researchers-devised-recaptcha.html