PS starts security mode?

My PS4 just starts in security mode and says I have to download an update manually and drag it to the console.

Yesterday I made them out as normal and today I made them as normal as I have been doing for 3 years. So nothing special.

What can I do now besides pulling this update?

I don't want to lose my data.

Is a PS4 slim if that is important.

I don't have a Playstation but as a computer scientist I would just do what it says.

Usually a software update is not the same as formatting all data.
I.e. A software update (whether OTA or manual) shouldn't be a problem.

Would agree with the other answer, do the update. If that doesn't work, I would just call support, they are the professionals after all.