An XSS Vulnerability exists in Webmin 1.941 and earlier affecting the Cluster Shell Commands Endpoint. A user may enter any XSS Payload into the Command field and execute it. Then, after revisiting the Cluster Shell Commands Menu, the XSS Payload will be rendered and executed.
An Improper Data Validation Vulnerability exists in Webmin 1.941 and earlier affecting the Command Shell Endpoint. A user may enter HTML code into the Command field and submit it. Then, after visiting the Action Logs Menu and displaying logs, the HTML code will be rendered (however, JavaScript is not executed). Changes are kept across users.
rpc.cgi in Webmin through 1.920 allows authenticated Remote Code Execution via a crafted object name because unserialise_variable makes an eval call. NOTE: the Webmin_Servers_Index documentation states "RPC can be used to run any command or modify any file on a server, which is why access to it must not be granted to un-trusted Webmin users."
In Webmin through 1.910, any user authorized to the "Package Updates" module can execute arbitrary commands with root privileges via the data parameter to update.cgi.
custom/run.cgi in Webmin before 1.870 allows remote authenticated administrators to conduct XSS attacks via the description field in the custom command functionality.
CSRF exists in Webmin 1.850. By sending a GET request to at/create_job.cgi containing dir=/&cmd= in the URI, an attacker to execute arbitrary commands.
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.