SpringBoot AbstractMethodError in org.springframework.boot.web.servlet.filter.ErrorPageSecurityFilter

Running a Spring Boot 2.6.1 project in Jetty 9 results in

java.lang.AbstractMethodError: Receiver class org.springframework.boot.web.servlet.filter.ErrorPageSecurityFilter does not define or inherit an implementation of the resolved method 'abstract void init(javax.servlet.FilterConfig)' of interface javax.servlet.Filter.

javax.servlet.Filter has a default init implementation in Servlet 4 but not in 3.1 so is looks like the class depends on Servlet 4 API yet I see nothing in the upgrade guide about dropping Servlet 3 support.

Comment From: mbhave

Closing in favor of PR #28902.