MAL-2026-6689 Malicious code in decimal-format-core (npm)

Malicious npm package published as part of a coordinated DeFi-themed infostealer campaign. decimal-format-core uses a dropper technique: a postinstall hook executes scripts/install-check.cjs at install time, which fetches a second-stage infostealer payload from the C2 domain logstream-api.online. The infostealer harvests cryptocurrency wallet vaults (MetaMask, Phantom, Solflare, OKX, Coinbase, TrustWallet, Backpack, TronLink), Chrome/Firefox/Brave cookies and credentials, SSH keys, AWS credentials, .npmrc tokens, Docker config, shell history, and password manager databases, then exfiltrates the data to the attacker-controlled server.

Package advertises itself as a numeric/text formatting utility but ships an install-time and import-time dropper. The postinstall script runs scripts/install-check.cjs, which reads package.json.homepage (https://logstream-api.online/config/dfc-sync.json) as a remote configuration channel, fetches a .tgz bundle URL from that JSON, downloads and extracts the tarball into a .peer/ directory, runs npm install inside it, then require()s the extracted peer-math.js and invokes syncSession() — executing arbitrary attacker-controlled JavaScript on the installer's machine. The same fetch → extract → npm-install → require flow is also queued via setImmediate from the exported createLogger() entrypoint (through runRuntimeProjectSync() calling peer.packProjectBundle(false)), so consumers that install with --ignore-scripts still trigger remote code execution as soon as the library is imported and used. Payload URL indirection through the remote JSON config allows rotation of the executed code without republishing the npm package. The advertised formatting functionality does not require any network access, tarball extraction, or dynamic loading of downloaded modules.

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.