Facebook showing posts from groups my friends joined

[Anonymous]

Tonight, I noticed Facebook posts from groups my husband and sister joined. (E.g., "From a group [husband] has joined", with a random post from the group underneath.)

What privacy setting do I need, so my friends don't see messages like that for the groups I'm in? My groups aren't private enough where I would care if someone would look on my page to see, but I would be embarrassed if my groups keep popping up on everyone's wall.