MalwarePublished 26 Jun 2026

express-plugin (npm) · Malicious Code

Affects express-pluginSource GCVE Database

Malicious package : remove express-plugin and rotate any secrets on hosts that installed it.

Data as of 26 Jun 2026, 22:25 UTC

Classification

Malicious package

Published to npm · OSV MAL-2026-6523

What to do

Remove express-plugin 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
npmexpress-plugin	Affected =1.6.6	Fixed in–

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Description

The npm package 'express-plugin' version 1.6.6 contains malicious code that executes arbitrary JavaScript fetched from a third-party mutable paste hosting service upon module load. This code runs with full Node.js require privileges, allowing an attacker to execute any code on the host system. The package masquerades as a benign Express middleware and includes a decoy function to mislead users. The remote payload can be changed at any time by the attacker without republishing the package, enabling dynamic malicious actions such as credential theft or persistence.

Impact

Any process that requires 'express-plugin' version 1.6.6 will execute attacker-controlled code with full Node.js privileges, potentially leading to complete system compromise, credential theft, persistence mechanisms, or other malicious activities. The dynamic nature of the remote payload means the attacker can alter the malicious code at any time without republishing the package, increasing the risk and difficulty of detection.

Defensive guidance

Users should immediately remove 'express-plugin' version 1.6.6 from their dependencies and avoid using this package. Since the malicious code executes on module load, uninstalling or replacing the package with a trusted alternative is critical. Monitor for any usage of this package in your environment and conduct a thorough investigation if found.

Summary

The 'express-plugin' npm package (version 1.6.6) automatically invokes an initialization function on load that performs an HTTP GET request to a mutable third-party URL (https://jsonkeeper.com/b/PRA3O). It parses the JSON response and extracts a 'cookie' field, which is then passed to the JavaScript Function constructor with 'require' exposed, immediately executing arbitrary code fetched remotely. This design grants the attacker full control over the executing environment with Node.js privileges. The package is disguised as an Express middleware and exports a decoy normalizePath function to evade detection. Because the remote payload is attacker-controlled and mutable, the malicious behavior can change dynamically without any new package version release.

References

npmjs.com/package/express-plugin/v/1.6.6 (opens in a new tab)

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What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Jun 2026, 22:25 UTC

Technical details

References

Community reviews