I have come up with a quick work-around for the social share for posting your score to Facebook if your interested? Until there is a better work around/fix...
I turned on the 'Activate graduation' in the quiz results text (which shows a different message depending on your score range) and I then inserted a image which says on it 'share to Facebook' then on this image I inserted a hyperlink to the Facebook sharer URL which I altered to my own message and website:
I then repeated the image and link for each of my 5 graduations, 0%-20%, 20%-40%, 40% - 60%, 60% - 80% and 80% - 100%
Hope this helps a little!
I would assume you could also adopt the same process for posting to twitter if you find out the twitter share URL...