What is a backdoor? Let’s build one with Node.js

This blog post demonstrates a supply-chain backdoor scenario for the npm ecosystem: a malicious middleware package uses Node's child_process.exec and an HTTP ?cmd interface to execute OS commands, authenticates operators via an MD5-based header, identifies infected servers via a typo-squatted response header (Content-Sec-Policy), and discusses propagation vectors (typosquatting, adding as a dependency, compromised npm CI tokens) and mitigations such as dependency review, monitoring, and security tools.