Since Multivatriate Quadratic(MQ)-based Public Key Cryptosystem(MPKC)has been one of the hot research fields of post-quantum cryptography,it becomes important to analyze the security of new MPKC schemes.Wang et al.proposed a novel multivariate signature scheme with Hash-based Tame Transformation and Minus(HTTM)in 2011.For this extended MQ-based signature,we can transform it into an SFLASH variant by splitting and merging HT transformation,and solve an equivalent private key corresponding to the public key of HTTM.Thus,the adversary can forge legitimate signature for any message by using this equivalent private key. Since Multivatriate Quadratic (MQ) -based Public Key Cryptosystem (MPKC) has been one of the hot research fields of post-quantum cryptography, it becomes important to analyze the security of new MPKC schemes. Wang et al .proposed a novel multivariate signature scheme with Hash-based Tame Transformation and Minus (HTTM) in 2011. For this extended MQ-based signature, we can transform it into an SFLASH variant by splitting and merging HT transformation, and solve an equivalent private key corresponding to the public key of HTTM .Thus, the adversary can forge legitimate signature for any message by using this equivalent private key.