void Document::writeln(const String& text, Document* ownerDocument, ExceptionState& exceptionState)
{
    write(text, ownerDocument, exceptionState);
    if (exceptionState.hadException())
        return;
    write("\n", ownerDocument);
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.