This release introduces a brand new feature: Burp Collaborator.
Burp Collaborator is an external service that Burp can use to help discover many kinds of vulnerabilities, and has the potential to revolutionize web security testing. In the coming months, we will be adding many exciting new capabilities to Burp, based on the Collaborator technology.
This release is officially beta due to the introduction of some new types of Scanner checks, and the reliance on a new service infrastructure. However, we have tested the new capabilities thoroughly and are not aware of any stability issues.