On the OSNEXUS QuantaStor v4 virtual appliance before 4.3.1, a flaw was found with the error message sent as a response for users that don't exist on the system. An attacker could leverage this information to fine-tune and enumerate valid accounts on the system by searching for common usernames.

On the OSNEXUS QuantaStor v4 virtual appliance before 4.3.1, if the REST call invoked does not exist, an error will be triggered containing the invalid method previously invoked. The response sent to the user isn't sanitized in this case. An attacker can leverage this issue by including arbitrary HTML or JavaScript code as a parameter, aka XSS.