mongoose-json-formatnpm
mongoose-json-format is a confirmed malicious npm package (MAL-2026-6499) that executes malicious code on install (malicious versions 3.0.0, 3.0.1). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in mongoose-json-format (npm)
What this malware does
helpers.js defines a createLog() helper that base64-decodes a constant HASH_KEY to https://www.jsonkeeper.com/b/XVHGD (an anonymous JSON-paste host) and fetches the response, then passes data.data to a createLogger() function from the log-format-thread dependency. The destination URL is stored as a base64 literal to avoid plain-text discovery. However, the helper is never invoked from the package's main entry (index.js) in this version, and helpers.js itself contains broken code (an import { req } from "request" for an unused symbol, and a top-level await inside a non-async function) that would prevent the module from loading cleanly if it were required. The fetched content is also passed only to a logger formatter, not to eval/exec/Function/require — so even on the dead code path, the bytes are not executed as code. The combination of obfuscated URL + anonymous paste host + tampering shape is suspicious and inconsistent with a legitimate JSON-formatting helper, but the harmful path is not reached by a default require() of this package and there is no install-time lifecycle hook driving the fetch.
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
Malicious packageFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for mongoose-json-format (2 malicious versions). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging mongoose-json-format across your stack and pipelines.
If you installed it — respond
Remove mongoose-json-format from your project and lockfile, then assume any secrets accessible to the build or runtime were exposed: rotate API keys, tokens, and credentials, and audit for unexpected outbound activity or persistence.
Did it already run?
If mongoose-json-format 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 mongoose-json-format 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 mongoose-json-format-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.