The postinstall script fetches YAML from https://chain-devkit.com/config with no version pin, hash, or signature check, then parses it with js-yaml 3.12.0's yaml.load, which honors!!js/function and!!js/regexp tags and constructs Function objects at parse time. The parsed object is written to chain.config.yaml and re-loaded at require() time via the same unsafe loader, giving whoever controls chain-devkit.com a live channel to inject arbitrary JavaScript Function objects into installer processes at every install and every require. Current index.js only reads scalar fields (chainId, rpcUrl, network), so code execution is not automatically triggered on today's config content, but the injected Function values persist in the on-disk config and would execute if any consumer or future package version invokes them. Publisher metadata is thin (atomicmail.io author email, fresh package with no history), and the destination host is controlled by the same anonymous publisher, so the fetch is effectively an attacker-controlled update channel bolted onto npm install.