Which versions of polyfill-corejs2 are malicious?

The following npm versions of polyfill-corejs2 are flagged malicious: 8.9.0, 8.9.1. Treat any of these as compromised.

How do I remediate polyfill-corejs2 if I installed it?

Remove polyfill-corejs2 from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.

I already installed polyfill-corejs2 — how do I know if it already compromised me?

If polyfill-corejs2 was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.

Is polyfill-corejs2 part of a known attack campaign?

Yes — polyfill-corejs2 is associated with the RLMA-2025-06450 campaign. Packages in the same campaign often share infrastructure and payloads, so check whether any related packages are also in your dependency tree.

How do I find polyfill-corejs2 across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for polyfill-corejs2 (2 malicious versions).

Malicious package

polyfill-corejs2npm

Advisory published Dec 23, 2025Updated Jan 2, 2026

polyfill-corejs2 is a confirmed malicious npm package (MAL-2025-192852) that executes malicious code on install (malicious versions 8.9.0, 8.9.1). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in polyfill-corejs2 (npm)

MAL-2025-192852

Immediate action

Remove the package, then rotate any secrets the build/runtime could reach.

npm uninstall polyfill-corejs2

What this malware does

The package polyfill-corejs2 was found to contain malicious code.

Malicious versions

2 flagged

8.9.08.9.1

Indicators of compromise (SHA-256)

d359e53d8e1d619f3e5b7ab1d604cf2e84cce3f772d93dd178177bd9e070632b

da972d0266a0a823fc38bb0bc6bf31a1d939a543c27322ece4ee07b11e36cf7b

Detection & response playbook

Malicious package

Find it
Search your lockfiles and build artifacts for polyfill-corejs2 (2 malicious versions).
If you installed it — respond
Remove polyfill-corejs2 from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.
Did it already run?
If polyfill-corejs2 was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.

Frequently asked questions

No. polyfill-corejs2 on npm has been identified as a malicious package (versions 8.9.0, 8.9.1 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

RLMA-2025-06450

Credits

Amazon Inspector · finder
ReversingLabs · finder

Detect & block this

O3 blocks polyfill-corejs2-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.

Malware detection Runtime egress monitoring

Explore

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