Unrestricted Upload of File with Dangerous Type
Kunena before 5.0.4 does not restrict avatar file extensions to gif, jpeg, jpg, and png. This can lead to XSS and remote code execution.
CWE-434 - Unrestricted Upload of File with dangerous type
'Unrestricted file upload with dangerous type' attacks involve an attacker uploading or transferring files of dangerous types to the server. The severity of such an attack depends upon the execution mechanism and the storage location of the uploaded file. Thus, it may range from simple defacement to arbitrary file execution, and complete system takeover.