Updated 2022-09-14: Critical Security updates for Concrete v8 will be issued through end 2023. More info - https://www.concretecms.org/about/project-news/security/security-support-concrete-v8x
When we released Concrete CMS version 9 in 2021 we promised to continue to release security updates for the 8.5.x branch until at least May 1st, 2022.
We are now extending that support period through December 31st, 2022.
We’d encourage you to upgrade your 8.5.x sites to v9 as soon as possible. Version 9 has a wealth of new usability features including a dramatically improved file manager. As always, take a backup first, but the upgrade path should be much simpler than many of our major version releases in the past. Onwards and upwards!