Archived version
Here is the report (pdf)
The supply chain attack targeting widely-used Polyfill[.]io JavaScript library is wider in scope than previously thought, with new findings from Censys showing that over 380,000 hosts are embedding a polyfill script linking to the malicious domain as of July 2, 2024.
This includes references to "https://cdn.polyfill[.]io" or "https://cdn.polyfill[.]com" in their HTTP responses, the attack surface management firm said.
"Approximately 237,700, are located within the Hetzner network (AS24940), primarily in Germany," it noted. "This is not surprising – Hetzner is a popular web hosting service, and many website developers leverage it."
Details of the attack emerged in late June 2024 when Sansec alerted that code hosted on the Polyfill domain had been modified to redirect users to adult- and gambling-themed websites. The code changes were made such that the redirections only took place at certain times of the day and only against visitors who met certain criteria.
The nefarious behavior is said to have been introduced after the domain and its associated GitHub repository were sold to a Chinese company named Funnull in February 2024.
The development has since prompted domain registrar Namecheap to suspend the domain, content delivery networks such as Cloudflare to automatically replace Polyfill links with domains leading to alternative safe mirror sites, and Google to block ads for sites embedding the domain.
[Edit typo.]