Amazon CloudFront will be adding enhanced domain protections to Amazon. The new measures are designed to ensure that requests handled by CloudFront are handled on behalf of legitimate domain owners. These new measures include enhanced protection against Domain Fronting and Dangling DNS entriess risk of dangling DNS entries pointing at other infrastructure you dont control. The best fix for this kind of risk is not to leave dangling DNS entries in the first place.”]
Source: https://aws.amazon.com/blogs/security/enhanced-domain-protections-for-amazon-cloudfront-requests/