Schools and universities across the country are recovering from an outage tied to a cyberattack that knocked down Canvas. The online platform manages exams, course notes, lecture videos and grades. The disruption hit in the middle of finals period for many colleges, a high-stress time when students and instructors rely heavily on the platform. Instructure is the parent company of Canvas and says the platform is available again to most users as of late Thursday. A threat analyst at the cybersecurity firm Emsisoft says the hacking group ShinyHunters claimed responsibility for the breach.