The Jetty component that is used for the HBase Stargate REST endpoint is version 6.1.26 and is fairly outdated. We recently had a customer inquire about enabling cross-origin resource sharing (CORS) for the REST endpoint and found that this older version does not include the necessary filter or configuration options, highlighted at: http://wiki.eclipse.org/Jetty/Feature/Cross_Origin_Filter
The Jetty project has had significant updates through versions 7, 8 and 9, including a transition to be an Eclipse subproject, so updating to the latest version may be non-trivial. The last update to the Jetty component in https://issues.apache.org/jira/browse/HBASE-3377 was a minor version update and did not require significant work. This update will include a package namespace update so there will likely be a larger number of required changes.