virtualenv: Downloaded seed wheels (pip/setuptools) are not integrity-checked before use
download_wheel() runs pip download and hands the result straight to the seeder, with nothing checking the bytes it gets back. The embedded pip and setuptools wheels carry a BUNDLE_SHA256 that virtualenv checks on every load, but a wheel fetched over the network for the periodic-update feature or the –download flag had no equivalent verification. A compromised index, a stale mirror, or a MITM'd download (when TLS is intercepted, e.g. via …