There's a setting that acts as a "ON/OFF switch" to keep Facebook apps and other websites from sharing or accessing your information. It's a useful trick that many people don't know about, especially if you want as much privacy as possible while maintaining your account.
It's called "Platform." It's the way third-party games (like Candy Crush) or websites ("Would you like to sign in using Facebook?") are integrated with your profile.
It allows not only the apps or sites you visit to access your data, but the apps and sites your Facebook friends visit as well.
This is how you turn it off:
First, go to the right hand corner and click "Settings":
Then, select "Apps" from the left hand side:
At the top of the screen, you'll see "Apps you use". If that feature says "On", you want to turn it off. Click "Edit":
Now you can turn off "Platform". Remember, this means you won't be able to log into websites or apps using Facebook, and friends won't be able to share information with you through apps.
Read before making your decision:
And ... you're done!
And no more apps sharing my info and post on my behalf...