Jenkins versions 2.56 and earlier as well as 2.46.1 LTS and earlier are vulnerable to an unauthenticated remote code execution. An unauthenticated remote code execution vulnerability allowed attackers to transfer a serialized Java `SignedObject` object to the Jenkins CLI, that would be deserialized using a new `ObjectInputStream`, bypassing the existing blacklist-based protection mechanism. We're fixing this issue by adding `SignedObject` to the blacklist. We're also backporting the new HTTP CLI protocol from Jenkins 2.54 to LTS 2.46.2, and deprecating the remoting-based (i.e. Java serialization) CLI protocol, disabling it by default.