A vulnerability classified as critical was found in Beijing Yunfan Internet Technology Yunfan Learning Examination System 1.9.2. Affected by this vulnerability is an unknown functionality of the file src/main/java/com/yf/exam/modules/sys/user/controller/SysUserControl of the component JWT Token Handler. The manipulation leads to improper authentication. The attack can be launched remotely. The complexity of an attack is rather high. The exploitation appears to be difficult. The exploit has been disclosed to the public and may be used.