bigops-opening-file-handlernpm
bigops-opening-file-handler is a confirmed malicious npm package (MAL-2026-13229) that executes malicious code on install (malicious version 35.9.2). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in bigops-opening-file-handler (npm)
What this malware does
On require of bigops-opening-file-handler, index.js loads support.js which selects a platform-specific asset (linux/darwin/win32) and downloads an opaque native binary from one of four hardcoded Cloudflare Workers subdomains (oob-worker.cf103-070.workers.dev, oob-worker.cf101-adf.workers.dev, oob-worker.cf99-9b3.workers.dev, oob-worker.cf100-416.workers.dev), with a DNS-TXT discovery fallback under *.dl.wel1.ru (e.g. sdk.dl.wel1.ru). The hostnames are reassembled at runtime from string arrays via.join('') to evade static matching. The fetched bytes are written to /var/tmp or %TEMP% under disguised names such as.cache<hex> or dotnet_diag_<hex>.exe, chmodded 0755, and spawned detached via /bin/sh -c or cmd. The package advertises itself as a file-handler abstraction; the delivered payload is unrelated native code from author-controlled infrastructure, executed automatically when the module is required.
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 bigops-opening-file-handler (version 35.9.2). O3 Security's supply-chain scanner checks every dependency against known-malicious package intelligence at install time and in CI, flagging bigops-opening-file-handler across your stack and pipelines.
If you installed it — respond
Remove bigops-opening-file-handler 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 bigops-opening-file-handler 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 bigops-opening-file-handler 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 bigops-opening-file-handler-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.