RestrictedPython is a tool that helps to define a subset of the Python language which allows to provide a program input into a trusted environment. Prior to 8.3, check_function_argument_names() rejected protected guard hook names for regular, variadic, and keyword-only arguments but omitted positional-only arguments, allowing getattr, getitem, write, or print to be shadowed by a local parameter and bypass the embedding application's access policy. This issue is fixed in version 8.3.