This is a security feature. Do not change this feature unless the scope of the change is fully understood. When allowHighBitCharacters ...

This is a security feature. Do not change this feature unless the scope of the change is fully understood. When allowHighBitCharacters is set to false (the value is true if not present), IIS rejects a request if it contains high-bit characters. If high-bit characters should be allowed by the server, modify the configuration/system.webServer/security/requestFiltering@allowHighBitCharacters setting.