Using additional extensions is another way of extending the functionality of your Plesk. Extensions are functional components developed by Plesk or third parties. Plesk partners offer a large number of additional Plesk extensions, which include antivirus protection software, advanced backup solutions, and much more.
If an extension requires an additional license key, you can obtain it from Plesk as described in the section Installing Additional License Keys for Plesk Add-ons. In some cases, you must obtain license keys for extensions from the extension developers.
Typically, third-party extensions are delivered as packages and can be easily installed, removed, and configured directly from Plesk (the Extensions item in the navigation pane).
To install additional extensions provided by Plesk, go to Extensions > Extensions Catalog, or visit the http://ext.plesk.com website.
You can also upload an additional extension not included into the Extensions Catalog as an .rpm or a .zip archive. To do this, go to Extensions and click the Add Extension button. Then select an archive with the extension and click OK.
Note: Installing extensions from untrusted sources is insecure.