Created in April 2017, unCaptcha achieved 85% accuracy defeating Google's ReCaptcha. After the release of this work, Google released an update to ReCaptcha with the following major changes:

Better browser automation detection
Spoken phrases rather than digits
These changes were initially successful in protecting against the original unCaptcha attack. However, as of June 2018, these challenges have been solved. We have been in contact with the ReCaptcha team for over six months and they are fully aware of this attack. The team has allowed us to release the code, despite its current success.