The "Submission Web Form" of Turnitin LTI tool/plugin version 1.3 is affected by HTML Injection attacks. The security issue affects the submission web form ("id" and "title" HTTP POST parameters) where the students submit their reports for similarity/plagiarism checks.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.