If users see the “System Extension Blocked” prompt when launching a Citrix Receiver desktop or application, they can go directly to System Preferences > Security & Privacy and Click Allow against Citrix Systems Inc as shown below to allow loading of the Citrix kernel extension: Citrix Receiver 12.7 for Mac requires Citrix kernel extension to be loaded for Generic USB Redirection to function properly. With macOS 10.13 High Sierra, Apple has introduced a new feature, where user approval is required to load any newly-installed third-party kernel extensions (KEXTs).
New users after installing Citrix Receiver 12.7 or above for Mac on macOS High Sierra when launching an application or desktop might get the following error:
