webpack-patchnpm
Advisory published Updated
webpack-patch is a confirmed malicious npm package (MAL-2026-5581) that opens a backdoor for remote access (malicious versions 1.1.7, 1.1.8, 1.1.9…). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in webpack-patch (npm)
What this malware does
Package impersonates the webpack ecosystem but is unrelated to webpack. When the exported middleware is invoked, index.js spawns a detached node lib/caller.js child. caller.js fetches https://jsonkeeper.com/b/XRGF3 via axios and passes the response's .cookie field to new Function.constructor('require', s)(require), executing attacker-controlled JavaScript with full Node privileges and a retry loop. The C2 URL and HTTP header name/value are stored as base64 strings under sham process.env keys (DEV_API_KEY base64-decodes to https://jsonkeeper.com/b/XRGF3); a sibling const.js variant points at https://jsonkeeper.com/b/4NAKK, providing pivot URLs if the primary paste is removed. jsonkeeper.com is an anonymous mutable paste host — whoever controls the paste controls arbitrary code execution on every consumer that loads webpack-patch and exercises its API. The package.json description is generic boilerplate copied from an unrelated security policy, and the main is a fake pino-style middleware whose only meaningful effect is launching the 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
Indicators of compromise (SHA-256)
Detection & response playbook
Backdoor / remote accessFind it
Search your lockfiles and build artifacts for webpack-patch (4 malicious versions).
If you installed it — respond
webpack-patch establishes remote access, so treat any host that installed it as fully compromised. Isolate the machine, remove the package, rotate all credentials it could reach, and rebuild from a trusted image rather than cleaning in place — a backdoor may have planted additional persistence.
Did it already run?
If webpack-patch 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
- ReversingLabs · finder
Detect & block this
O3 blocks webpack-patch-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the C2 callback and severs the channel.