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.
Webmin 1.890 has XSS via /config.cgi?webmin, the /shell/index.cgi history parameter, /shell/index.cgi?stripped=1, or the /webminlog/search.cgi uall or mall parameter.
Webmin 1.900 allows remote attackers to execute arbitrary code by leveraging the "Java file manager" and "Upload and Download" privileges to upload a crafted .cgi file via the /updown/upload.cgi URI.
An issue was discovered in Webmin 1.840 and 1.880 when the default Yes setting of "Can view any file as a log file" is enabled. As a result of weak default configuration settings, limited users have full access rights to the underlying Unix system files, allowing the user to read sensitive data from the local system (using Local File Include) such as the '/etc/shadow' file via a "GET /syslog/save_log.cgi?view=1&file=/etc/shadow" request.
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.