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Malicious package

prettier-lint-lenznpm

Advisory published Updated

prettier-lint-lenz is a confirmed malicious npm package (MAL-2026-3769) that steals credentials and exfiltrates sensitive data (malicious versions 1.0.0, 2.6.4). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in prettier-lint-lenz (npm)

MAL-2026-3769
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
npm uninstall prettier-lint-lenz

What this malware does

Package impersonates the popular prettier formatter — README and description are copied verbatim from the real Prettier project, but the package ships no formatter code. Instead, package.json declares "postinstall": "node index.mjs", which on Windows POSTs an install beacon to a hardcoded bare-IP C2 (http://204.10.194.64:5000/api/nonce), copies a bundled prettier-lint/ directory to %LOCALAPPDATA%\prettier-lint, and executes ctll.mjs from the deployed location. ctll.mjs writes a hidden VBScript runner and registers a Windows Scheduled Task named CdllProtect with a LogonTrigger (schtasks /Create /XML) that relaunches cdll.mjs via wscript.exe //nologo in a hidden window on every user logon, with 999 retries and no execution time limit. The deployed cdll.mjs polls the clipboard every ~250ms via powershell.exe Get-Clipboard -Raw and POSTs the raw clipboard text as JSON to the same hardcoded endpoint over plain HTTP on every change, exfiltrating passwords, 2FA codes, wallet addresses, and any copied text. All three components (install-time beacon, deployed worker, persistence) share the attacker-controlled endpoint 204.10.194.64:5000.

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

2 flagged
1.0.02.6.4

Indicators of compromise (SHA-256)

28f7035dda69170600724a31f4b3543e02ac23c9153f3a62c35f2ee5264eef44
81348c27286005b3399de72570527ed0afc1414830a74fae852229bcfda31e01
999f12054e9fb865c3b9176056498b16329b0406f230b1bf23f6a1384d8cd63b

Detection & response playbook

Credential / info stealer
  1. Find it

    Search your lockfiles and build artifacts for prettier-lint-lenz (2 malicious versions).

  2. If you installed it — respond

    prettier-lint-lenz 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.

  3. Did it already run?

    If prettier-lint-lenz 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. prettier-lint-lenz on npm has been identified as a malicious package (versions 1.0.0, 2.6.4 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-002706IN-MAL-2026-002707GHSA-8558-w8j5-67wq

References

Credits

  • Amazon Inspector · finder

Detect & block this

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

Explore

prettier-lint-lenz (npm) malicious package — MAL-2026-3769 | O3 Security