With the development of new information and communication technologies such as developments related to Internet of Things applications, the importance of information and maintaining its security is more and more considered. Key agreement and authentication protocols play an important role in ensuring information security. One of the important components used in many applications of the Internet of Things is wireless sensor networks, whose security is ensured by using appropriate protocols of these networks. In 2020, Sikarwar and Das presented a key agreement protocol with authentication for wireless sensor networks and claimed that this protocol is secure against well-known attacks such as feedback attacks, password discovery, and man-in-the-middle attacks. In this paper, it is shown that the Sikarvar and DOS protocol is not secure and an attacker can easily obtain this key. In addition, it is shown that the protocol cannot be secure against password discovery and spoofing attacks.