A sandbox bypass vulnerability exists in Script Security Plugin 1.49 and earlier in src/main/java/org/jenkinsci/plugins/scriptsecurity/sandbox/groovy/GroovySandbox.java that allows attackers with the ability to provide sandboxed scripts to execute arbitrary code on the Jenkins master JVM.
https://www.exploit-db.com/exploits/46572/
https://www.exploit-db.com/exploits/46453/
https://jenkins.io/security/advisory/2019-01-08/#SECURITY-1266
https://access.redhat.com/errata/RHBA-2019:0327