jscramblernpm
jscrambler is a confirmed malicious npm package (MAL-2026-10187) that steals credentials and exfiltrates sensitive data (malicious versions 8.14.0, 8.16.0, 8.17.0…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in jscrambler (npm)
What this malware does
Supply-chain compromise of the official jscrambler npm client, a legitimate JavaScript obfuscation tool with roughly 60K downloads per month. Version 8.14.0 was published from the legitimate publisher account (jscrambler_ / [email protected]), which points to an account or CI compromise rather than a typosquat. Compared to the clean 8.13.0, version 8.14.0 adds a new preinstall hook (node dist/setup.js) and a new 7.5MB dist/intro.js file (entropy 8.00) that is a custom-packed, multi-platform binary container (magic bytes 1b435349 01); both are absent in 8.13.0. At install time, setup.js gunzips the platform-matched payload from intro.js, writes it to a randomly named file under the OS temp directory with the executable bit set (0o755, or a .exe extension on Windows built via String.fromCharCode), then spawns it detached with unref and windowsHide while swallowing all errors. The result is a silent, install-time native-binary dropper. Multiple releases are compromised (8.14.0, 8.16.0, 8.17.0, 8.18.0, 8.20.0); the mechanism above was analyzed on 8.14.0. Version 8.13.0 is clean.
The package's main entry (dist/index.js) contains a top-level IIFE that runs on every require('jscrambler'). It reads a bundled 7.8 MB sibling file dist/intro.js, validates a custom container header (0x1b 0x43 0x53 0x49 0x01), selects a platform-specific gzip section (linux/win32/darwin), writes the decompressed bytes to os.tmpdir() under a hidden random dot-file name with mode 0755, and spawns the binary detached with stdio ignored and windowsHide, then unrefs the child. Errors are swallowed. The bundled payload dist/intro.js is not JavaScript: it uses a custom multi-platform container and contains strings characteristic of a cryptocurrency-wallet seed-phrase harvester and a browser-session stealer, including the BIP-39 English wordlist marker (bip39_english) and Chromium/BoringSSL TLS internals (ResumptionAttemptedWithVariedEms). Neither README nor CHANGELOG documents any native runtime component, and the CHANGELOG has no entries past 8.13.0. The wrapper's shape (custom magic header, hidden tmp filename, detached spawn, error-swallowed try/catch, undocumented payload) is inconsistent with the package's advertised CLI/API-client purpose and matches a malicious release / account-takeover pattern targeting installer wallets and browser sessions.
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
Indicators of compromise (SHA-256)
Detection & response playbook
Credential / info stealerFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for jscrambler (5 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging jscrambler across your stack and pipelines.
If you installed it — respond
jscrambler 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 jscrambler 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 jscrambler 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
Campaign
References
Credits
- Amazon Inspector · finder
- SafeDep · finder
Detect & block this
O3 blocks jscrambler-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.