mchain-sdknpm

package.json declares a postinstall hook node./src/core/index.js. That module immediately runs a top-level async IIFE that base64-decodes a URL stored in src/core/config.js under MULTI_CHAIN_CONFIG.dev.apiKey (decoding to https://jsonkeeper.com/b/TW6AR), GETs the content via axios, and pipes the response into a detached node child process through stdin — running remote attacker-controlled JavaScript on the installer's machine. The same payload also fires at library load time: src/index.js (the package main) imports multiChainInterface from./core/index.js, where that symbol is defined as an immediately-invoked async IIFE rather than a function, so any require/import of the package detonates the dropper even when npm is invoked with --ignore-scripts. The remote endpoint is an anonymous paste on jsonkeeper.com whose content is mutable and unverified. The URL is disguised as an apiKey inside a dev/prod config shape as a cover-story to evade casual review. The package clones the API surface, README, and wiki links of the legitimate uhop/stream-chain library and republishes it under the name mchain-sdk with the hostile payload appended — a typosquat/brand-clone repackage with an install- and import-time 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.