Webmin before 1.860 has XSS with resultant remote code execution. Under the 'Others/File Manager' menu, there is a 'Download from remote URL' option to download a file from a remote server. After setting up a malicious server, one can wait for a file download request and then send an XSS payload that will lead to Remote Code Execution, as demonstrated by an OS command in the value attribute of a name='cmd' input element.
