The following phenomenon may occur due to irregularities on an optical layer located in front of the image sensor: White spots may exist on the optical layer which may result in the appearance of dark circular patterns on the captured image under certain shooting conditions. -- Canon

Since the problem is indeed serious, Canon's published a product advisory to help those of you who own a T6s or T6i find out if your camera is affected. What's more, the company says any potentially defective units are going to be inspected and, if need be, repaired at no cost to people. Canon didn't mention whether there's a plan to recall the flawed models, but did say more details will be shared as soon as possible. "At this time, we offer our apologies to any customer who might have been inconvenienced. We are actively looking into solutions to fix any issues related to this advisory," a Canon spokesperson told Engadget.