Why am I seeing Facebook statuses of people I don't know in my news feed?

When a Facebook friend of mine likes or comments on one of their friends statuses, the entire conversation now appears in my news feed.

It used to only appear in the ticker, and if you were a nosy person you could click on the ticker and see the entire conversation.

I’m assuming complete strangers are now looking at my status when a mutual friend comments on or likes it. How can I fix the privacy for this? Do I need to ask everyone to go to the trouble of clicking on this and clicking on that just so their friends (people I don’t know or people I may not like) don’t see my posts? ugh