The refactoring present in Apache Tomcat 9.0.28 to 9.0.30, 8.5.48 to 8.5.50 and 7.0.98 to 7.0.99 introduced a regression. The result of the regression was that invalid Transfer-Encoding headers were incorrectly processed leading to a possibility of HTTP Request Smuggling if Tomcat was located behind a reverse proxy that incorrectly handled the invalid Transfer-Encoding header in a particular manner. Such a reverse proxy is considered unlikely.
https://www.oracle.com/security-alerts/cpuoct2020.html
https://www.oracle.com/security-alerts/cpujul2020.html
https://www.oracle.com/security-alerts/cpujan2021.html
https://www.debian.org/security/2020/dsa-4680
https://www.debian.org/security/2020/dsa-4673
https://security.netapp.com/advisory/ntap-20200327-0005/
https://lists.debian.org/debian-lts-announce/2020/03/msg00006.html
http://lists.opensuse.org/opensuse-security-announce/2020-03/msg00025.html