https://support.atlassian.com/confluence/kb/confluence-fails-to-start-due-to-proxyservlet-has-been-compiled-by-a-more-recent-version-of-the-java-runtime/
Confluence fails to start due to "ProxyServlet has been compiled by a more recent version of the...
Confluence fails to start due to "ProxyServlet has been compiled by a more recent version of the Java Runtime": How to troubleshoot and fix