A sandbox bypass vulnerability exists in Pipeline: Declarative Plugin 1.3.3 and earlier in pipeline-model-definition/src/main/groovy/org/jenkinsci/plugins/pipeline/modeldefinition/parser/Converter.groovy that allows attackers with Overall/Read permission to provide a pipeline script to an HTTP endpoint that can result in arbitrary code execution on the Jenkins master JVM.
https://www.exploit-db.com/exploits/46572/
https://jenkins.io/security/advisory/2019-01-08/#SECURITY-1266
https://access.redhat.com/errata/RHBA-2019:0327