In a build which contains an activeChoice checkbox param, there is a problem when the build is triggered by a push or any event that don't give any parameters.

If the script that provide the checkbox list is in sandbox mode, then a default value of the environnement variable is filled with the first item value.

Exemple with this simple Jenkinsfile :

pipeline {
    agent any
    parameters {
      activeChoice(name: 'environnements', choiceType: 'PT_CHECKBOX', filterLength: 1, filterable: false, script: groovyScript(script: [sandbox: true, script: "return ['devA','devB','devC']", classpath: []]))
    }
    stages {
        stage('Hello') {
            steps {
                echo 'Parameters :'
                sh "env -0 | sort -zfi | tr '\\0' '\\n' | sed 's/^/    /'"
            }
        }
    }
}
 

The log provide to the environnements envvar the value "devA".

environnements=devA

Nota : By setting the sandbox to "false", this behaviour disappear and all is OK but not secured.