PrivacyPass is an extension that lets you pre-solve CloudFlare CAPTCHAs if you're on a VPN. However, that was too frustrating, so CloudFlare partnered with Apple to integrate PrivacyPass into Safari.
How did they do this? Simple: iOS provides cryptographic attestation that your browser isn't a bot and isn't hacked, and CloudFlare takes that as your CAPTCHA solution. This works exactly the same way that Google proposes Web Environment Integrity work.
