How to update ios 13 in my iphone 6

You can not, as it is not compatible with iOS 13 or higher.

What does this mean for users of iPhone 6 with regards to the security fix that is in IOS 14?

The vulnerability only affects iOS 13 & 14. If you are running 12.5.4 or older, you are immune.

Only phones running iOS 13 or higher were are risk of the vulnerability. Since you're on iOS 12, you are not in danger and this was validated by Apple.

Lucky for them the Pegasus exploit only affects iPhones running iOS 13 and 14.

The security update is for iOS 13 and 14. You do not need to worry about your phone.

Thanks!

You're welcome.

Thanks for the feedback.