Cryptanalysis of Zhang-Xiao's multisignature scheme for specified group of verifiers

Recently, Zhang-Xiao proposed a new multisignature scheme for specified group of verifiers. However, Zhang-Xiao's scheme is still susceptible to forgery attack. Accordingly, the current paper demonstrates the vulnerability of Zhang-Xiao's scheme to fogery attack that an attacker can forge the multisignature for any message.