Worth grepping your source code for "polyfill.io" and taking urgent measures to remove that code if you're linking it into your site - the domain name apparently now intermittently serves malicious JavaScript
My notes here: https://simonwillison.net/2024/Jun/25/polyfill-supply-chain-attack/ - or read this article https://sansec.io/research/polyfill-supply-chain-attack