PDF files can literally carry viruses. Seems like you don't know much about Internet security. Maybe educate yourself on the topics you wish to discuss before commenting on them. PDFs are a rich text format which can execute macros, javascript, embeded executables, ect. and infect machines. There are several types of ransomware which exploit that fact. Regardless, QR codes themselves are an exploitable format and there is absolutely no reason this game or any other "needs" to use them other than to track player statistics and information and besides the potential malware vector I have no interest in being part of unnecessary data collection.