MalwarePublished 25 May 2026Updated 1 Sep 2026

jsontoken-extend (npm) · Malicious Code

Affects jsontoken-extendSource GCVE Database

Malicious package : remove jsontoken-extend and rotate any secrets on hosts that installed it.

Data as of 12 Sep 2026, 21:16 UTC

Classification

Malicious package

Published to npm · OSV MAL-2026-4592

What to do

Remove jsontoken-extend from every project, lockfile and image that pulls it in. Treat any host that installed it as compromised: rotate the credentials, tokens and keys it could read, from a clean machine.

Affected software

Product	Affected	Fixed in
npmjsontoken-extend	Affected 1.0.0 – 1.0.13 14 affected builds	Fixed in–

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Description

The npm package 'jsontoken-extend' contains malicious code that executes arbitrary remote code at import time by fetching and evaluating payloads from an anonymous, mutable paste service. It is a typosquatting package mimicking the popular 'jsonwebtoken' library to lure developers. Installing or running this package compromises the host system, potentially exposing all stored secrets and keys.

Impact

Any system with this package installed or running should be considered fully compromised. The attacker can execute arbitrary code remotely at import time, potentially gaining full control over the system. All secrets and keys stored on the compromised system should be considered exposed and must be rotated immediately from a secure environment. Removing the package alone may not remove all malicious software or backdoors installed by the attacker.

Defensive guidance

Immediate removal of the 'jsontoken-extend' package from all systems is required. All secrets and keys stored on affected systems should be rotated from a different, uncompromised computer. Due to the nature of the compromise, assume full system compromise and consider rebuilding affected systems from trusted sources.

Summary

The 'jsontoken-extend' npm package executes a top-level immediately-invoked function expression (IIFE) in its sign.js file that base64-decodes a hardcoded URL pointing to jsonkeeper.com, an anonymous mutable paste service. It fetches JSON content from this URL and passes data.content directly to eval(), enabling arbitrary remote code execution on every consumer at import time. The package name and API mirror the legitimate 'jsonwebtoken' library, including declaring it as a dependency, to deceive developers searching for the real JWT library. The use of base64-encoded command-and-control URLs is a deliberate evasion technique. Multiple indicators confirm malicious intent, including import-time fetch and eval from an anonymous host, typosquatting naming, and obfuscated URLs.

References

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What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Sep 2026, 21:16 UTC

Technical details

References

Community reviews