There is no automated script or anything else that will automagically upgrade your CF8 to any later version. And I hate to be the bearer of bad news, but you're most likely going to have to update your CF8 code (especially if upgrading to CF11 or CF2016.)
PS. The good news is that ever since CF10, application security has vastly improved. I highly recommend (if you haven't already) studying ESAPI and implementing use.