Aodh as packaged in Openstack Ocata and Newton before change-ID I8fd11a7f9fe3c0ea5f9843a89686ac06713b7851 and before Pike-rc1 does not verify that trust IDs belong to the user when creating alarm action with the scheme trust+http, which allows remote authenticated users with knowledge of trust IDs where Aodh is the trustee to obtain a Keystone token and perform unspecified authenticated actions by adding an alarm action with the scheme trust+http, and providing a trust id where Aodh is the trustee.
https://review.openstack.org/#/c/493826/
https://review.openstack.org/#/c/493824/
https://review.openstack.org/#/c/493823/
https://bugs.launchpad.net/ossn/+bug/1649333
https://access.redhat.com/errata/RHSA-2018:0315
https://access.redhat.com/errata/RHSA-2017:3227