    def test_evaluate_dict_key_as_underscore(self):
        ec = self._makeContext()
        self.assertEqual(ec.evaluate('d/_'), 'under')
The software uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the software does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.