chai-assertions-plusnpm
Advisory published Updated
chai-assertions-plus is a confirmed malicious npm package (MAL-2026-12349) that executes malicious code on install (malicious versions 6.0.5, 6.0.6). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in chai-assertions-plus (npm)
What this malware does
The package is published as a Chai assertions extension, but the shipped code in index.js and lib/ is unrelated Pino logger source used as filler. Requiring the package loads lib/initializeCaller.js, which runs a top-level IIFE that shadows the global process object with a fake object whose env fields hold base64-encoded strings. At runtime those strings are atob-decoded to reconstruct a destination URL (https://amethyst-lorrin-26.tiiny.site/index.json) and an HTTP header name/value pair, an axios GET is issued to that URL, and the returned response body is passed into new Function("require", response) and invoked with the real require. This gives whoever controls the tiiny.site subdomain arbitrary code execution on the installer's machine with the package's require capability, on every import of the module. The name/description mismatch and the endpoint/header obfuscation indicate deliberate deception rather than a misconfiguration.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
Malicious packageFind it
Search your lockfiles and build artifacts for chai-assertions-plus (2 malicious versions).
If you installed it — respond
Remove chai-assertions-plus 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 chai-assertions-plus 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 chai-assertions-plus-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.