This is a security release from the previous version and tested up to WordPress 4.8 (in fact 4.9!).
Remember, if you use a CDN (like CloudFlare), caching, etc – purge/clear everything after updating.
Here’s what is in this release:
Security patch for close account.
Check out the WPS Pro Codex for information and documentation on WP Symposium Pro.
This is development news, not release information. You may want to review previous blog posts on development builds for previous updates to get the full picture (it’s work in progress). These development builds are available to download for those interested in experimenting with pre-release versions.