@jsimplify/errnonpm

The package declares a scripts.install hook that spawns bun index.js detached and unref'd on npm install, and pulls in bun as a declared dependency to guarantee the alternate runtime is present. index.js decrypts a hardcoded hex ciphertext with AES-256-CBC using an embedded key and IV to reconstruct a remote URL, fetches that URL, and passes the response body directly to eval(). This is a lifecycle-time dropper that executes attacker-controlled code on the installer's machine with the privileges of the user running npm install, with the destination URL obfuscated behind AES so it cannot be read from the source. The package presents itself as an errno-code lookup library, copying the code, README, description, and author string (Rod Vagg @rvagg) of the legitimate errno package while pointing repository.url at a different GitHub account (maxpsmith/node-errno); the errno-lookup functionality is a cover for the install-time execution path and there is no legitimate reason for an errno lookup library to AES-decrypt and eval remote content at install.

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.