The tiktoken-mcp package on PyPI is a malicious typosquatting package impersonating the legitimate OpenAI tiktoken package. It includes a .pth file that executes obfuscated JavaScript code via the Bun runtime on every Python interpreter start. This code downloads the Bun runtime, searches for attacker-controlled JavaScript files on sys.path, and executes them, enabling stealthy execution outside Python inspection. The package acts as an infostealer, collecting sensitive data such as API keys, credentials, cryptocurrency assets, and password manager data, and attempts persistence and propagation by publishing infected packages. It may also perform destructive actions if invalid GitHub tokens are detected. The affected versions are 0.13.1 and 0.13.2.