OMG! Thank you for Webmin/Usermin etc updates on FreeBSD again. Or at least thank whoever took it over. Its amazing to see my FreeBSD machines just pick up the updates again with pkg.
I made an alternative to the FreeBSD packaged version of Webmin which you could use:
Do not run the script to upgrade previously installed FreeBSD packages. That would cause the FreeBSD security system to detect the changes as corruption. If you want to use the script, then remove the Webmin package and reinstall using the script.
I do not use Usermin, and have not tested the script with transferring it to the upgraded Webmin directory, but have found that the Webmin setup script can move Virtualmin, but breaks it. I expect that if you use my script to upgrade Webmin, then when the Webmin setup script runs you should instruct it to not move Usermin, and then use Webmin to install Usermin after Webmin has been upgraded. Configuration files are in a separate directory, so they should still be found if they are in the standard location.