You may receive an email informing you when you authorize an app.
If you get an email saying you've authorized an app that you don't recognize, go to the My Apps page in your account. There you will see the header for "Connected Apps" which will show any apps you've connected to your account.
If you don't recognize an app, you can (and should) easily remove it from your account.
Finally, if you have any questions, don't hesitate to contact us!