The 3.12.13 MongoDB Java Driver release is a patch to the 3.12.12 release and a recommended upgrade.
The documentation hub includes extensive documentation of the 3.12 driver, including
- What’s New : what’s new in the 3.12 driver
- Upgrading : upgrading from the 3.11.x driver
- Installing MongoDB Driver : how to get the Java driver.
and much more.
You can find a full list of bug fixes here.