The system of multiple sets of question papers was reintroduced after two years and the sets were not only reordered but some had up to 30% new questions. Some papers even had more than three sets. Question papers also came with QR codes to trace the origin of a leak and stop its spread. The board tracked exam centre superintendents carrying papers to the centres.

from Times of India https://timesofindia.indiatimes.com/home/education/news/multiple-papers-qr-codes-live-tracking-how-cbse-plugged-paper-leaks-this-year/articleshow/68588388.cms