Unauthorized creation of master key in Mifare Classic Be-Tech cards

The data stored in Be-Tech Mifare Classic card is stored in cleartext. An attacker having access to a Be-Tech hotel guest Mifare Classic card can create a master key card that unlocks all the locks in the building. This issue affects all Be-Tech Mifare Classic card systems. To fix the vulnerability, it is necessary to replace the software, encoder, cards, and PCBs in the locks.