we use Gitlab 15.10.7-ee as CE till now, only for internal access. I thinkfull to update to 16 version, but for now everything working fine. I know and understand that the update are improtant but what you think, if the platform is using only for a few users internaly is this mandatory
For security reasons yes. Some would say with it being accessible only internally the risk is less. Which is somewhat true, although a user could end up with their system being compromised which could then compromise your server.
At the end of the day it’s up to you. If publicly accessible I would definitely do it and apply updates immediately as they come available. For internal use, you have a bit more time as the risk is somewhat less for it being compromised.
Good practice is to update, especially if there are critical CVE’s which need to be addressed.