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Yup.

It looks like it is running the service that was part of the supply chain attacker earlier this year. https://github.com/polyfillpolyfill/polyfill-service/issues/...

The service was fine, it was the "official" hosted instance of the service which was compromised. IA appears to be running their own instance.

That was a DNS hack of polyfill.io though right? This looks like it was/is self hosted.

Yeah I'm getting this exact response from the above URL now:

Seems like they self hosted that service

Correct. The source subdomain of the popup seems to be hxxps[:]//polyfill[.]archive[.]org