Apple has determined that, in a small percentage of iPhone 6 Plus devices, the iSight camera located on the back of your iPhone 6 Plus has a component that may fail causing your photos to look blurry.
The affected units fall into a limited serial number range and were sold primarily between September 2014 and January 2015.
If your iPhone 6 Plus is producing blurry photos and falls into the eligible serial number range, Apple will replace your device’s iSight camera, free of charge.
If your iPhone 6 Plus is in working order and exhibits the symptom described above, use the serial number checker to see if it is eligible for this program. Tap Settings > General > About to see your iOS device’s serial number.
More info and Apple’s serial number checker here.
Source: Apple Inc.