After upgrading from 2.426 to 2.427 stdout and stderr is no longer returned to the client.

I started a fresh Jenkins, and created an admin account, downloaded the jenkins-cli.jar and ran a simple command, that should write Hello! on the terminal.

docker run -p 8080:8080 jenkins/jenkins:2.427-jdk17
wget http://localhost:8080/jnlpJars/jenkins-cli.jar
echo 'println "Hello!"' | java -jar jenkins-cli.jar -auth admin:admin -s http://localhost:8080/ groovy =

It appears to be related til https://issues.jenkins.io/browse/JENKINS-41516, and creating a logger for jenkins.util.DefaultScriptListener results in rather large stacktraces everytime any output is generated for a script.