GHSA-rpj2-4hq8-938g: VCR.py: Arbitrary code execution via unsafe YAML deserialization of cassette files

vcrpy deserializes YAML cassette files with PyYAML’s object-constructing loader (yaml.CLoader / yaml.Loader) instead of the safe loader (yaml.CSafeLoader / yaml.SafeLoader). A cassette containing a !!python/object/apply: (or similar) tag therefore executes arbitrary Python code the moment the cassette is loaded — including through the normal VCR().use_cassette() path, before any HTTP interaction is replayed.

This is not limited to environments lacking the libYAML C extension. CLoader uses the C parser but PyYAML’s full Python constructor, so Python object tags execute under CLoader exactly as under the pure-Python Loader. Confirmed against vcrpy 8.1.1 + PyYAML 6.0.3 with CLoader active.