I passed a long day dealing with Jenkins runtime update (from jdk17 to jdk21), and authorisation plugin (Matrix Auth) stopping to work. Here is the tale. Involved system: Error log messages was related to hudson, and to matrix, and to authorization: Caused: jenkins.util.xstream.CriticalXStreamException: [LF]> —- Debugging information —-[LF]> cause-exception : com.thoughtworks.xstream.mapper.CannotResolveClassException[LF]> cause-message : hudson.security.GlobalMatrixAuthorizationStrategy[LF]> class […]