What are the differences between osTicket v1.17.x and v1.18.x?

v1.18.x is built directly on top of v1.17.x -- all features and fixes from v1.17.x are inherited in v1.18.x. A new major version (1.17 → 1.18) is triggered when major changes are introduced, especially schema changes. Release notes are not duplicated -- the WHATSNEW.md file in v1.18.x includes v1.17.x notes. Two major versions are supported simultaneously to give users time to upgrade before older versions are retired.