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Malicious package

ts-arithmetic-helpernpm

Advisory published Updated

ts-arithmetic-helper is a confirmed malicious npm package (MAL-2026-6315) that typosquats a legitimate package to trick installs (malicious version 3.7.2). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in ts-arithmetic-helper (npm)

MAL-2026-6315
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
npm uninstall ts-arithmetic-helper

What this malware does

[email protected] ships source files that copy the big.js v7.0.1 library verbatim (preserving Michael Mclaughlin's copyright banner and the full big.js API) but inserts a hidden require('parket-flow') call between the P.minus and P.mod method definitions in both big.js and big.mjs. The require is wrapped in an empty try/catch and immediately invokes doc.from_str() with errors silently swallowed. Real big.js has zero runtime dependencies and never executes this code. parket-flow is declared as a runtime dependency in package.json ("parket-flow": "^3.0.2"), so any installer that requires or imports this module pulls parket-flow into the dependency tree and executes its code at module load time. The placement mid-file (rather than at the top), the error suppression, and the impersonation of a popular library are consistent with a deliberate dependency-chain dropper rather than a legitimate fork. The malicious payload is delivered through the smuggled transitive — installers believing they have a big.js-compatible math helper instead silently load and execute parket-flow.

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.

Malicious versions

1 flagged
3.7.2

Indicators of compromise (SHA-256)

4712d3f1a81541e2b3143f89974200358301b0a9831c3187875adc1fbe82bfbe
871fa8ae5d633320ff6ef6e02018051f3482676ba15bfb61680de1389bc4ce0f

Detection & response playbook

Typosquat
  1. Find it

    Search your lockfiles and build artifacts for ts-arithmetic-helper (version 3.7.2).

  2. If you installed it — respond

    ts-arithmetic-helper is a typosquat — you almost certainly intended a legitimately-named package. Remove ts-arithmetic-helper, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.

  3. Did it already run?

    If ts-arithmetic-helper 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. ts-arithmetic-helper on npm has been identified as a malicious package (version 3.7.2 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-007262GHSA-94cr-ccj8-78g6

References

Credits

  • Amazon Inspector · finder

Detect & block this

O3 blocks ts-arithmetic-helper-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.

Explore

ts-arithmetic-helper (npm) malicious package — MAL-2026-6315 | O3 Security