youngnawab on "All Posts loading Unknown Script"

hi there,my all posts are loading a unknown script : http://rankboostup.com/plugin/content.js .
Is it malware or something.i am not familiar with this script.i Deactivated all plugins but still loading that script,i can not find injected script in my functions.php or single.php files,how to detect exact location and remove this script from my site. my site url is lyricsraag.com