This is a major release, which brings a few new features and bugfixes as usual, but this one also fix some security issues (CVE-2021-41262, CVE-2021-41261, CVE-2021-41260).
Upgrade is highly recommended.
- Social networks/contact externalization
 - Add member number
 - Export contributions as CSV
 - Drop group name uniqueness at same level
 - Add CSRF protection
 - Enhance groups managers capacities
 - …
 
See Galette 0.9.6 changelog for all details.
Unfortunately, some required background changes (CSRF checks) has made almost all plugins incompatible, and it is required to update them, see plugins documentation ;-)
Hope you will enjoy this release; happy Galette!