Very strange. Anyone else having the same problem?/
Well it would have helped if you gave us any information on which phone you have and which update your phone received.
Yah, I'm sure it would. I found the answer a nano second later:
http://www.urtech.ca/2013/12/solved-samsung-s3-android-4-3-camera-flashes-with-inbound-email-or-phone-calls/
Galaxy S3, latest version on Android (this week)
