CVE-2021-28163: Directory exposure in jetty

Impact

If the ${jetty.base} directory or the ${jetty.base}/webapps directory is a symlink (soft link in Linux), the contents of the ${jetty.base}/webapps directory may be deployed as a static web application, exposing the content of the directory for download.

For example, the problem manifests in the following ${jetty.base}:

demo-base/
├── etc
├── lib
├── resources
├── start.d
├── deploy
│   └── async-rest.war
└── webapps -> deploy

Workarounds

Do not use a symlink