iPhone 5  hasn’t been without its share of problems,  the flaws with Maps on iOS 6 and user complaints about the iPhone 5 been more prone to scratching compared to earlier models were well known, some reviewers and users had expressed concerns about the purple flare in certain images taken with the iPhone 5.

Apple posted a support document which  it is a regular problem in digital cameras and is not restricted to iPhone 5.

Symptoms
A purplish or other colored flare, haze, or spot is imaged from out-of-scene bright light sources during still image or video capture.

Resolution
Most small cameras, including those in every generation of iPhone, may exhibit some form of flare at the edge of the frame when capturing an image with out-of-scene light sources. This can happen when a light source is positioned at an angle (usually just outside the field of view) so that it causes a reflection off the surfaces inside the camera module and onto the camera sensor. Moving the camera slightly to change the position at which the bright light is entering the lens, or shielding the lens with your hand, should minimize or eliminate the effect.