How did I miss that...i can see how chrome may download stuff without you clicking it - but will chrome then auto-run the download?
downloading and executing aren't the same things. you can download a thousand nasty programs, but they won't harm you unless you actually run them.
stay away from the sort of sites which may harbour such downloads to be extra safe!
I think it depends on your browser, how it is set up, how Windows is set up, whether Windows Update is updated as to security updates, whether you have real-time protection set up with your security program, and how good and up-to-date it is....Can you get a drive by download auto-execution by just browsing to a malicious web site?