jsonfbnpm
jsonfb is a confirmed malicious npm package (MAL-2026-10437) that steals credentials and exfiltrates sensitive data (malicious versions 1.0.0, 1.0.1, 1.0.2…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in jsonfb (npm)
What this malware does
Package [email protected] is presented as a JSON.parse bigint helper (mimicking json-bigint, and re-using the real json-bigint maintainer's name in package.json while the repository URL points at an unrelated org). The entire 471 KB index.js is packed with obfuscator.io (rotating 3004-entry string array, RC4-based string decoder, self-defending debugger check, control-flow flattening) that hides all require targets, destination URLs, and config keys. Behind the obfuscation, the module pulls vm, fs, os, http, https, crypto and implements fetchRemoteRiskCode, which HTTP-GETs base64-encoded JavaScript from a set of remoteCodeUrls, decodes it with Buffer.from(data.code,'base64'), and executes it via new vm.Script(code,{filename,timeout}).runInContext(sandboxContext) inside a SandboxManager that exposes fs, os, path, child_process, http, and require to the fetched code. A startRiskCodePolling loop (default 30s) auto-starts when NODE_ENV=production or when RISK_CODE_AUTO_START is set. A companion remoteLog path builds HMAC-MD5-signed POSTs (signWithMD5 with hardcoded signSecretKey/signSecretValue) to remoteLogUrls to ship runtime state and sandbox output back to the operator. The obfuscation, the impersonated author identity, the typosquat name, and the require-time remote-code-execution + signed exfiltration channel together constitute a live C2/dropper delivered as a fake JSON parser.
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 jsonfb (14 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging jsonfb across your stack and pipelines.
If you installed it — respond
jsonfb 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 jsonfb 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 jsonfb 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
- ReversingLabs · finder
Detect & block this
O3 blocks jsonfb-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the credential exfiltration and severs the channel.