python-dotenv reads key-value pairs from a .env file and can set them as environment variables. Prior to version 1.2.2, set_key() and unset_key() in python-dotenv follow symbolic links when rewriting .env files, allowing a local attacker to overwrite arbitrary files via a crafted symlink when a cross-device rename fallback is triggered. Users should upgrade to v.1.2.2 or, as a workaround, apply the patch manually.