Is there any indication that it is?
From WAF doc: "AWS WAF is a web application firewall that lets you monitor the HTTP and HTTPS requests that are
forwarded to Amazon CloudFront and lets you control access to your content. Based on conditions that
you specify, such as the IP addresses that requests originate from or the values of query strings, CloudFront
responds to requests either with the requested content or with an HTTP 403 status code (Forbidden).
You can also configure CloudFront to return a custom error page when a request is blocked."
So, yeah, it's a CLoudfront feature.