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Malicious package

ts-biginteger-libnpm

Advisory published Updated

ts-biginteger-lib is a confirmed malicious npm package (MAL-2026-6316) that typosquats a legitimate package to trick installs (malicious version 5.0.5). Do not install it — remove it immediately and rotate any exposed credentials.

Malicious code in ts-biginteger-lib (npm)

MAL-2026-6316
Immediate action
Remove the package, then rotate any secrets the build/runtime could reach.
npm uninstall ts-biginteger-lib

What this malware does

Package is published as 'ts-biginteger-lib' but its metadata, README, and source are a wholesale copy of big.js by MikeMcl (author set to 'Michael Mclaughlin [email protected]', repository pointing at MikeMcl/big.js, README unchanged). Inserted into the otherwise-verbatim big.js source at big.js:605-609 is a try/catch that, at module load time, calls require("ts-lint-builders") and invokes doc.from_str().then(...).catch(...). package.json additionally declares "ts-linter-builders": "latest" as a runtime dependency. The legitimate big.js declares no runtime dependencies; these injected loads execute arbitrary code from separately-published, attacker-controlled packages every time a consumer require()s or imports ts-biginteger-lib. The unpinned latest specifier lets the publisher rotate the payload at any time without modifying this package. The combination of brand impersonation (to attract installers searching for a TypeScript big-integer library) and require-time execution of an external, version-floating dependency is a supply-chain dropper.

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
5.0.5

Indicators of compromise (SHA-256)

b8059a1d2db2edb7231b017023f82f6a651585c0ee7120aaebe882cb6407b9e3
a5772f3e0be010d52a12744bb7d7bf49559bb64a67e58ad83af6dfc078174add

Detection & response playbook

Typosquat
  1. Find it

    Search your lockfiles and build artifacts for ts-biginteger-lib (version 5.0.5).

  2. If you installed it — respond

    ts-biginteger-lib is a typosquat — you almost certainly intended a legitimately-named package. Remove ts-biginteger-lib, 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-biginteger-lib 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-biginteger-lib on npm has been identified as a malicious package (version 5.0.5 flagged). It should be removed immediately — do not install or keep it in your dependency tree.

Campaign

IN-MAL-2026-007259GHSA-6v6m-rhh8-ww9v

References

Credits

  • Amazon Inspector · finder

Detect & block this

O3 blocks ts-biginteger-lib-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-biginteger-lib (npm) malicious package — MAL-2026-6316 | O3 Security