If your plugin is not code signed, Windows may identify your plugin as a potential risk for some users and display a warning prompt.
The best way to fix this issue is to sign your plugin and installer using a code signing certificate, a feature Temasys offers. Temasys can sign the binaries and/or the installer, with either your code signing certificate, or, if you choose, with Temasys'.
In case of any further queries, please contact the Temasys Sales Team.
Please note that even after the signing, you may still see a Windows warning message as you're about to run the install: Why do I see a "not commonly downloaded, may harm your computer" warning on IE when I install my custom plugin?