fpjson-langnpm
fpjson-lang is a confirmed malicious npm package (MAL-2026-4566) that steals credentials and exfiltrates sensitive data (malicious version 0.1.7). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in fpjson-lang (npm)
What this malware does
package.json declares "preinstall": "./bin/install-deps", causing npm to execute a ~954KB packed Linux ELF binary on every install. The package advertises itself as a tiny JSON-based functional language built on Ramda, and the actual library at dist/cjs/index.js is ~1.8KB of pure JavaScript with no native dependency — there is no legitimate reason for a native install helper. Strings extracted from the shipped binary include HTTP/1.1, POST/DELETE verbs, GitHub API version 2022-11-28, USERPROFILE, TLS/crypto primitives (RSA_PKCS1_, Ed25519), PTRACE, and LIBBPF_0.0 — a feature set (HTTP client + GitHub API + ptrace + crypto) wholly unrelated to a JSON parser. The binary is packed and opaque to static review. The combination of (a) auto-execution at install time via preinstall, (b) shipped opaque native binary, (c) capability set entirely unrelated to the package's declared purpose, and (d) absent source/build manifest matches the install-time dropper pattern: arbitrary attacker-controlled code runs on every installer's machine on npm install.
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.
This package was compromised as part of the IronWorm campaign. This campaign executes a malicious binary payload during installation via a preinstall hook. The payload is a Rust-built infostealer that targets developer environments, scanning for and harvesting credentials related to cloud providers, object storage, databases, source-control, package registries, and AI developer tools. It also targets cryptocurrency wallets, specifically injecting a malicious JavaScript hook into the Exodus desktop wallet to capture passwords and recovery phrases. Furthermore, the malware exhibits worm-like behavior by stealing GitHub and NPM credentials to push malicious updates to the victim's repositories and publish trojanized packages, and it uses an eBPF-based kernel rootkit to hide its processes and network connections on Linux systems.
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 fpjson-lang (version 0.1.7). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging fpjson-lang across your stack and pipelines.
If you installed it — respond
fpjson-lang 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 fpjson-lang 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 fpjson-lang 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
Detect & block this
O3 blocks fpjson-lang-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.