1. Canned messages usage statistic collecting option. Can be activated in statistic configuration tab. `Collect canned messages usage statistic`
2. Security fixes. All these were CSFR based issues which does not have much usage in real life scenario unless you account is already compromised. None of them are related to action which could be coused by visitor visiting your website. Update is still recommended. 
3. Integrated https://www.abstractapi.com/ip-geolocation-api as geo detection provider.

For update just follow standard update procedure For manual update it's update_252.sql and update_251.sql