Hackers build a ‘Master Key’ that can be used to unlock doors and gain entry to any of hotel rooms without leaving a trace on the system. The vulnerability has been discovered in Vision by VingCard locking system, used in 42,000 facilities in 166 different countries. Hackers can read the data remotely by standing close to a guest or employee having a keycard in his pocket, or simply could book a room and then use that card as the source. The attacker would then need to buy a portable programmer for a few hundred dollars online to overwrite it, and therefore creating a master key.
Source: https://thehackernews.com/2018/04/hacking-hotel-master-key.html