The 2.3.0 system update was released on May 15, 2017. This update was released for all regions.
Security flaws fixed: unknown.
This is the official changelog from Nintendo regarding this update:
Improvements Included in Version 2.3.0
- General system stability improvements to enhance the user's experience
It's unknown exactly what titles were updated.
The System Version Info title 0100000000000809 is the only title updated which is browser-accessible.
The browser was not updated.