this plugin used by hackers

this plugin has been used by hackers on my blog. even tho I have never uploaded, or installed any plugins from nmedia.
now I got all these links to my blog that lead to an error page. yet when source tracked down the google search led to a cached link with an overlay,(bad stuff). when viewing the source whoever copied my source page and added a doubled doc type to the html.
I cannot figure out how to block this. not in robots.txt nor the .httaccess. one of them used this nmedia to add a fake link to a fake plugin and a storifyupload php.