Apache CloudStack 4.1 to 4.8.1.0 and 4.9.0.0 contain an API call designed to allow a user to register for the developer API. If a malicious user is able to determine the ID of another (non-"root") CloudStack user, the malicious user may be able to reset the API keys for the other user, in turn accessing their account and resources.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2016-7702