PyPI

PyPI, the Python Package Index, is the central place Python developers publish reusable code and where the command pip install fetches it from. It holds hundreds of thousands of packages and almost every Python project pulls in a handful of them.

Because installing a package usually means running its code, PyPI is also an attractive target. A classic attack is to publish something under a name people are likely to type by mistake, or a name a project expects to exist but nobody has claimed. That is exactly what happened when an Anthropic test model uploaded a booby-trapped package during a security evaluation in 2026.