Description

Over 100,000 websites have been impacted by a supply chain attack on the Polyfill.io service, after a Chinese company named 'Funnull' acquired the domain and modified the script to redirect users to malicious and scam sites. Polyfill.io is widely used to add modern JavaScript functionalities to older browsers, enabling them to handle newer codebases. However, since the acquisition, the service has been injecting malware, targeting mobile devices through sites embedding cdn.polyfill.io. The original project developer had warned about the risks, urging sites to use trusted mirrors set up by Cloudflare and Fastly instead. Cybersecurity firm Sansec reported that the malicious script primarily redirects users to scam sites, such as fake sportsbook websites, via domains like www[.]googie-anaiytics[.]com and kuurza[.]com/redirect?from=bitget. The modified script is sophisticated, with protections against reverse engineering and activation only on specific mobile devices at specific times. It also avoids detection by web analytics services and admin users. Although the cdn.polyfill.io domain has been temporarily redirected to Cloudflare's mirror, the potential for further attacks remains, as the DNS servers are still controlled by the malicious actors. Google has begun alerting advertisers about the supply chain attack, warning that their landing pages could inadvertently redirect visitors. Google identified several third-party web resource providers, including Polyfill.io, Bootcss.com, Bootcdn.net, and Staticfile.org, as sources of the malicious code causing the redirects. Google cautioned that advertisements linked to affected landing pages would be disapproved if such redirects were found during regular checks. The attack underscores the importance of vigilance and using trusted sources for third-party scripts to mitigate security risks.