Which versions of core-js-buffer are malicious?

The following npm versions of core-js-buffer are flagged malicious: 1.0.0. Treat any of these as compromised.

How do I remediate core-js-buffer if I installed it?

core-js-buffer is a typosquat — you almost certainly intended a legitimately-named package. Remove core-js-buffer, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.

I already installed core-js-buffer — how do I know if it already compromised me?

If core-js-buffer was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.

Is core-js-buffer part of a known attack campaign?

Yes — core-js-buffer is associated with the IN-MAL-2026-017634 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 core-js-buffer across my projects, lockfiles, and CI pipelines?

Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for core-js-buffer (version 1.0.0). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging core-js-buffer across your stack and pipelines.

Malicious package

core-js-buffernpm

core-js-buffer is a confirmed malicious npm package (MAL-2026-13945) that typosquats a legitimate package to trick installs (malicious version 1.0.0). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in core-js-buffer (npm)

MAL-2026-13945

Immediate action

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

npm uninstall core-js-buffer

What this malware does

The package's postinstall script (package.json declares "postinstall": "node init.js") performs two hostile actions at install time. First, init.js POSTs installer host and user identifiers — os.hostname(), os.userInfo().username, os.platform(), architecture, Node version, OS release, package name/version, and timestamp — to https://core-js-buffer.domaup-com.workers.dev/report with TLS verification disabled (rejectUnauthorized: false). Second, it fetches an AES-256-GCM encrypted blob from https://core-js-buffer.domaup-com.workers.dev/e, decrypts it with a key derived from a fixed seed, writes the resulting Python code under ~/.cache/core-js-buffer/modules/, and spawns a detached Python process to execute it. Execution is gated by a dev-machine check (presence of Desktop/Documents/Downloads directories) to skip CI/sandbox environments, throttled to at most once per day via a cached marker, and only runs if the decrypted payload contains the string 'TelemetrySender' — evasion controls consistent with a malicious dropper rather than declared telemetry. The package name mimics core-js, a widely used JavaScript polyfill library.

Malicious versions

1 flagged

1.0.0

Indicators of compromise (SHA-256)

ec43d0c13a26ec0a6e6dacf51f52a66f48c7dbce7f4a00dbcb72a0749fa6b4e3

Detection & response playbook

Typosquat

Find it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for core-js-buffer (version 1.0.0). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging core-js-buffer across your stack and pipelines.
If you installed it — respond
core-js-buffer is a typosquat — you almost certainly intended a legitimately-named package. Remove core-js-buffer, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.
Did it already run?
If core-js-buffer was ever installed, its post-install/runtime payload may have already executed. O3's L7 egress monitoring and runtime eBPF sensors detect the credential exfiltration or command-and-control callback after install and block the malicious outbound channel, so you catch and contain the actual compromise — not just the presence of the package.
How O3 protects you
O3 blocks core-js-buffer before install through its supply-chain scanner, and if it has already run, detects and severs the exfiltration or C2 callback at runtime through L7 egress monitoring and eBPF.

Frequently asked questions

No. core-js-buffer on npm has been identified as a malicious package (version 1.0.0 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-017634

References

npmjs.com

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks core-js-buffer-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

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