I've been using iPhones since the first iPhone. I don't sync any relevant stuff to iCloud. However, during previous iOS updates this sync turned itself back on

I've been using iPhones since the first iPhone. I don't sync any relevant stuff to iCloud. However, during previous iOS updates this sync turned itself back on multiple times (more than three times for sure). It hasn't happened for a while but whenever there's an iOS update it's advisable to check your iCloud settings immediately afterwards and if they changed, you change them back and pray that your important data hasn't been sent to the cloud in the meantime.