This vulnerability exists in ZKTeco WL20 due to hard-coded private key stored in plaintext within the device firmware. An attacker with physical access could exploit this vulnerability by extracting the firmware and analyzing the binary data to retrieve private key stored in the firmware of the targeted device. Successful exploitation of this vulnerability could allow the attacker to perform unauthorized decryption of sensitive data and Man-in-the-Middle (MitM) attacks on the targeted device.