    def test_build_attr(self):
        assert set(ClearableFileInput().build_attrs({}).keys()) == {
            "class",
            "data-url",
            "data-fields-x-amz-algorithm",
            "data-fields-x-amz-date",
            "data-fields-x-amz-signature",
            "data-fields-x-amz-credential",
            "data-fields-policy",
            "data-fields-key",
        }
        assert ClearableFileInput().build_attrs({})["class"] == "s3file"
        assert (
            ClearableFileInput().build_attrs({"class": "my-class"})["class"]
            == "my-class s3file"
        )
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.