The npm package sigchain-js versions 1.0.0 and 1.0.1 contain malicious code in their published distribution bundles. These bundles include top-level code that decrypts an encrypted payload from companion packages and executes it via a spawned detached Node.js child process. This behavior enables arbitrary code execution on the host machine when the package is imported or required. The malicious payload is split across cooperating packages, including a dependency named thedata and a transitively included package tchain-api, which mimics an official SDK. Additionally, the package pins a non-existent axios version, redirecting installs to a squatted package. This threat does not have a known patch or fix at this time.