Sometimes you will run into an Java error whenever you use Webmin’s File Manager module. The error will look like below when using a Firefox browser.
Webmin file manager error Java couldn’t trust server
On the Mac open System Preferences then click the Java (Java icon)control panel.
Then under General click on settings.
Uncheck keep temporary files on my computer the click delete files. Click OK and apply.
This time you should be able to open the file manager. When you get this prompts just click continue.
Then click run.
You should be able to see the file manager open this time.