I had the very same issue, and now have removed everyone’s right to vote and am using my vote only. You can do the same using the star rating that resides beside wp edit window, and then if you want your viewers to see your rating on your page/post, there is a shortcode stated in that same box where you can add only your own rating.
Seems some reputation management companies are trying to change honest low ratings given to some products online. Where this was done on my website, I automatically made MY vote less than the one star given previously.
Those same hackers tried nearly 200 times to hack my site’s SQL scripting. Discontinuing letting others vote was my only option. Works for me!
Hope this helps you.
