A family picture that Zuckerberg's sister Randi posted on her personal Facebook profile was then tweeted on Twitter – by a friend of a friend.
The image shows the Zuckerberg family in their kitchen and it appeared in the “newsfeed” of one of her sisters. However, the privacy settings on the photo enabled Callie Schweitzer, a marketing director who is a friend of the sister, to see it and she posted it on Twitter.
That did not sit well with Randi, who tweeted at Schweitzer that the picture was meant for friends only.
Ms Schweitzer replied by saying the picture popped up on her Facebook newsfeed.
Ms Zuckerberg said Ms Schweitzer was able to see the picture because they had a mutual friend and that reposting it was “way uncool”. Those tweets have since been taken down.
“Not sure where you got this photo. I posted it to friends only on Facebook,” she warned Ms Schweitzer.
Ms Zuckerberg said she was annoyed about the incident because it was “not about privacy settings, it’s about human decency”.
"I'm just sensitive to private photos becoming 'news'," she added.
Facebook critics frequently accuse the site of making users share more than they intend to and that privacy settings are too complicated.