The CloudStack management server and secondary storage VM could be tricked into making requests to restricted or random resources by means of following 301 HTTP redirects presented by external servers when downloading templates or ISOs. Users are recommended to upgrade to version 4.18.1.1 or 4.19.0.1, which fixes this issue.
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.