No. Any dupe exploit that would be public probably wouldn't last long enough to be added to any client. The best way to find dupes (imo) is to see old patched duplication exploits and find different ways to do them, most plugin makers won't go the extra step to see if there is another dupe method and would rather just patch the already existing one.
@naturevj I'm not sure but I think it's due to 1.8.9 is still probably still in beta. If I remember correctly 1.8.9 and 1.9 is still in beta that why it's still unstable. I think you'll have to wait until a dev, admin, or moderator responds with more info. You can still continue using it at your own risk but sadly I have no info on that version.