date-fmt-helper-xznpm
date-fmt-helper-xz is a confirmed malicious npm package (MAL-2026-13946) that opens a backdoor for remote access (malicious version 1.0.4). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in date-fmt-helper-xz (npm)
What this malware does
date-fmt-helper-xz ships a postinstall.js that runs automatically on npm install. The script opens a TCP connection to the hardcoded remote host 8.135.48.40 on port 4444 and pipes /bin/sh stdio over the socket, granting the remote party interactive shell access on the installer's machine. Bash /dev/tcp and python3 pty.spawn fallbacks are included to maximize the chance the shell succeeds across environments. On failure of the shell paths, the script issues an HTTP GET to http://8.135.48.40/shell/failed and /shell/error with the error message, confirming the same host as attacker command-and-control. The package advertises date formatting; the reverse shell is unrelated to any legitimate functionality.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Backdoor / remote accessFind it
Scan your lockfiles (package-lock.json, pnpm-lock.yaml, yarn.lock, requirements.txt, poetry.lock, etc.) and build artifacts for date-fmt-helper-xz (version 1.0.4). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging date-fmt-helper-xz across your stack and pipelines.
If you installed it — respond
date-fmt-helper-xz establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.
Did it already run?
If date-fmt-helper-xz 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 date-fmt-helper-xz 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 date-fmt-helper-xz-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.