Polyfill supply chain attack hits 100K+ sites
sansec.io
The new Chinese owner of the popular Polyfill JS project injects malware into more than 100 thousand sites.

Archived link

The polyfill.js is a popular open source library to support older browsers. 100K+ sites embed it using the cdn.polyfill.io domain. Notable users are JSTOR, Intuit and World Economic Forum. However, in February this year, a Chinese company bought the domain and the Github account. Since then, this domain was caught injecting malware on mobile devices via any site that embeds cdn.polyfill.io. Any complaints were quickly removed (archive here) from the Github repository.

  • dan@upvote.auEnglish
    7·
    5 months ago

    This will have been pulled in as a dependency in many projects and the site either works or does not based on the presence of the bundle.

    This wasn’t bundled. People inserted a script tag pointing to a third-party CDN onto their sites. The output changes depending on the browser (it only loads the polyfills needed for the current browser) so you can’t even use a subresource integrity hash.