This happens in consulting and engineering a lot. Case interviews and problems are known among fellow students who are interviewing later, and questions get put up on glassdoor too. You will have to iterate around the problem. This is unavoidable aspect. Shell Recruitment Day problems are known in detail online, their online assessment test is copied and solved in detail. Shell hires lot of engineers, and good ones. Consulting firms hold one of most intensive and competitive interviews. Questions will leak, issuing these moral statements will not help, this is your problem to solve.