It is in accessibility settings. I found that the box was not checked on my phone. I checked it and the flashing continued. Once I unchecked it again, it was fine. Must be a default setting that has to be turned off again.
Re: AT&T Galaxy S3 4.3 Update Likes/Issues
I am also having the same problem. Anyone fix it yet? Also, how do I keep the camera flash from flashing during incoming calls??