An unrestricted file upload vulnerability exists in Kaseya KServer versions prior to 6.3.0.2. The uploadImage.asp endpoint allows unauthenticated users to upload files to arbitrary paths via a crafted filename parameter in a multipart/form-data POST request. Due to the lack of authentication and input sanitation, an attacker can upload a file with an .asp extension to a web-accessible directory, which can then be invoked to execute arbitrary code with the privileges of the IUSR account. The vulnerability enables remote code execution without prior authentication and was resolved in version 6.3.0.2 by removing the vulnerable uploadImage.asp endpoint.