decimal-format-utilsnpm
Malicious code in decimal-format-utils (npm) Remove it immediately and rotate any exposed credentials.
What this malware does
The postinstall script scripts/sync-peer.cjs runs npm pack [email protected] (or whatever version is configured via BACKUP_TARGET_VERSION/BACKUP_PAYLOAD_SPEC), extracts the resulting tarball, overwrites every file of the installed v1.0.0 package in place via fs.cpSync over the package root, and then require()s the replaced index.js and awaits from_str(). The effect is that npm install [email protected] executes code from a different, publisher-mutable version at install time, bypassing lockfile pinning and giving the publisher a live remote code execution channel into every install. The package additionally impersonates the big.js maintainer: package.json sets author: Michael Mclaughlin and repository.url: https://github.com/MikeMcl/big.js.git, and the README falsely claims the package is pulled in automatically as a dependency of [email protected]. big.js declares no such dependency. The impersonation appears designed to lure installers into trusting an unrelated publisher whose postinstall then executes arbitrary fetched code.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
TyposquatFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for decimal-format-utils (version 1.0.0). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging decimal-format-utils across your stack and pipelines.
If you installed it — respond
decimal-format-utils is a typosquat — you almost certainly intended a legitimately-named package. Remove decimal-format-utils, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.
Did it already run?
If decimal-format-utils 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 decimal-format-utils 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 decimal-format-utils-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.