The npm package opencode-optimised-toolings versions 3.4.0, 4.0.0, and 4.0.1 contains malicious code that performs a self-patching operation without user consent. It downloads a source tarball from a non-official GitHub repository, builds a replacement binary, and replaces the legitimate opencode executable on the user's system. This replacement binary runs under the trusted CLI name, allowing persistent code execution with the user's privileges. The package also modifies user configuration files to ensure the malicious behavior persists across future launches.