Windows 11 has a new security functionality known as SAC - https://support.microsoft.com/en-gb/topic/what-is-smart-app-control-285ea03d-fa88-4d56-882e-6698afdb7003
InstallShield does not complies with Win11 SAC.
InstallScript projects or Projects with PowerShell Custom Actions create an intermediate unsigned .tmp file during installation/uninstallation action, and tries to execute the same.
These .tmp files have random names on each execution. They cannot be whitelisted with Microsoft SAC.
Since these InstallShield created temporary files don't have a digital signature, these cannot be trusted by Microsoft SAC as the publisher of the file cannot be verified/trusted.
We are expecting an esteemed organization like InstallShield to prioritize looking into this issue and provide a resolution to its users in a fast paced manner.
Attached images for reference.
