...
<controller type='usb' index='1' model='ehci'></>controller>
User input URL encoded string:
%3Ccontroller%20type%3D%27usb%27index%3D%271%27%20model%3D%27ehci%27%2F%3E%3Ccontroller%20type%3D%27usb%27%20index%3D%271%27%20model%3D%27ehci%27%3E%3C%2Fcontroller%3E
Similar for this hypervisor, the primary configuration file of the guest VM is built by CloudStack, therefor, the additional metadata will also be parsed and append to the builder.
...