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Malicious package

bigops-opening-file-handlernpm

Advisory published Updated

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)

MAL-2026-13229
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
npm uninstall bigops-opening-file-handler

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

1 flagged
35.9.2

Indicators of compromise (SHA-256)

9c423840bea5711af66c8f9c24eca1c406a4fa929dc6b9e9d947ec71ea5adc39

Detection & response playbook

Malicious package

  1. Find it

    Search your lockfiles and build artifacts for bigops-opening-file-handler (version 35.9.2).

  2. 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.

  3. Did it already run?

    If bigops-opening-file-handler was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.

Frequently asked questions

No. bigops-opening-file-handler on npm has been identified as a malicious package (version 35.9.2 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-015767

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.

Malware detection Runtime egress monitoring

Explore

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bigops-opening-file-handler (npm) malicious package — MAL-2026-13229 | O3 Security