Apache Tomcat 9.0.0.M1 to 9.0.0.17, 8.5.0 to 8.5.39, and 7.0.0 to 7.0.93 are vulnerable to cross-site scripting because the SSI printenv command echoes user provided data without escaping. Note: SSI is disabled by default. The printenv command is intended for debugging and is unlikely to be present in a production website.
View the template here CVE-2019-0221.yaml
References:
https://seclists.org/fulldisclosure/2019/May/50