Polyfill Detected

high Web App Scanning Plugin ID 114357

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Synopsis

Polyfill Detected

Description

The `polyfill.js` file is a popular open-source library to ensure old browsers compatibility when evaluating JavaScript code. Starting February 2024, the domain `polyfill.io` and the related GitHub account have been purchased by a malicious threat actor to inject malwares in all web applications relying on, at least, the `cdn.polyfill.io` domain. The `polyfill.js` file cannot be trusted anymore as the malicious code could have been redistributed on other CDNs or locally copied in various plugins.

Solution

Remove the detected file(s) immediately from the web application if they are embedded in it, and ensure that the script is not loaded from any untrusted external source. Some vendors have already put some mitigations in place to rewrite content using the malicious `polyfill.io` domain or to serve a safe version of the library.