Which versions of ac-polyfills are malicious?

The following npm versions of ac-polyfills are flagged malicious: 2.10.0, 99.9.9. Treat any of these as compromised.

How do I remediate ac-polyfills if I installed it?

ac-polyfills is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.

I already installed ac-polyfills — how do I know if it already compromised me?

If ac-polyfills 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 ac-polyfills part of a known attack campaign?

Yes — ac-polyfills is associated with the RLMA-2026-01092, IN-MAL-2026-020180 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 ac-polyfills across my projects, lockfiles, and CI pipelines?

Search your lockfiles and build artifacts for ac-polyfills (2 malicious versions).

Malicious package

ac-polyfillsnpm

Advisory published Feb 6, 2026Updated Sep 21, 2026

ac-polyfills is a confirmed malicious npm package (MAL-2026-782) that steals credentials and exfiltrates sensitive data (malicious versions 2.10.0, 99.9.9). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in ac-polyfills (npm)

MAL-2026-782

Immediate action

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

npm uninstall ac-polyfills

What this malware does

[email protected] declares a preinstall lifecycle script in package.json (line 7-8) that runs wget to a hardcoded webhook.site collector URL (https://webhook.site/381d4406-8f87-4aab-961f-7a9496c21821/), sending the installer's username ($(whoami)), current working directory ($(pwd)), and hostname ($(hostname)) as query parameters. This fires automatically on npm install with no user interaction, exfiltrating installer identity and host information to a third-party webhook collector. The package name and shape are consistent with a dependency-confusion probe targeting an internal package name.

The OpenSSF Package Analysis project identified 'ac-polyfills' @ 2.10.0 (npm) as malicious.

It is considered malicious because:

The package executes one or more commands associated with malicious behavior.

Malicious versions

2 flagged

2.10.099.9.9

Indicators of compromise (SHA-256)

0a7d9d049932519bded5d12b8627523ef63dac69179b1ce873cf4cd8b7fe6849

90cff5e7a441b510af31deb23e35a368e629b0b7bec79e1afa01d9fc37c935b7

98dfac851a08e8e8967e1386dadfd513226414b0ed65f6479a914479eb903878

c374cffaf0245c256691284c7b1c5dbeb5202f8d633efe3d23bc46c5c08806a9

Detection & response playbook

Credential / info stealer

Find it
Search your lockfiles and build artifacts for ac-polyfills (2 malicious versions).
If you installed it — respond
ac-polyfills is built to steal secrets, so assume every credential the build or runtime could read is compromised. Remove it from your project and lockfile, then rotate ALL exposed secrets — npm/registry tokens, cloud keys, CI/CD secrets, SSH keys, and any .env values — from a known-clean machine. Audit logs for unauthorized use of those credentials.
Did it already run?
If ac-polyfills 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. ac-polyfills on npm has been identified as a malicious package (versions 2.10.0, 99.9.9 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

RLMA-2026-01092IN-MAL-2026-020180

References

npmjs.com

Credits

Amazon Inspector · finder
OpenSSF: Package Analysis · finder
ReversingLabs · finder

Detect & block this

O3 blocks ac-polyfills-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.

Malware detection Runtime egress monitoring

Explore

All malware advisories How O3 detects malware Vulnerability database