May 8 (UPI) -- Online education platform Canvas suffered a ransomware attack that shut down access in the United States on Thursday. Canvas, used by more than 8,000 schools and universities in the United States, is owned by parent company Instructure. It has more than more than 30 million active users globally. The site was working again for most users by late Thursday, Instructure said. But many schools had already changed their finals schedules to accommodate the shutdown. Universities like