It’s tough to resist the temptation to find out who among your acquaintances is straight-up done with you. This is why apps like Who Unfollowed Me for Twitter or Friend or Follow for Instagram are so popular.
Recently, developers unveiled a similar app for Facebook -- Who Deleted Me -- which gained so much viral traction that a flood of new users caused it to experience temporary outages. While hundreds of thousands of people flocked to the app to see who they were going to be mad at irl, however, some users speculated that it may steal vital information from your Facebook account.
Only apps that have been authorized by Facebook are secure
There are a whole bunch of apps that interface with your Facebook account, and the legit ones -- like Spotify, Airbnb, etc. -- are all run through something called Facebook’s API (Application Programming Interface). By doing so, these apps comply with Facebook’s terms of service, and will not gather any information that you have not specifically authorized.
“All developers building apps that integrate with Facebook, requesting information about people, must use a Facebook API, which ensures that people maintain control over who is accessing their information," a Facebook spokesperson told MTV News. "We take action against any app that violates our terms and policies.”
The "Who Deleted Me" app is NOT using Facebook's API
...which means that it is operating in violation of Facebook's policies. Facebook has contacted the developers and asked them to remove it.
If an app doesn’t ask for your permission to access aspects of your account, that’s a good sign it’s not secure
When you authorize a secure app, it will ask you if it can use information that is relevant to what it needs in order to run. This is why certain apps will ask if they can use your photos, music likes, or -- in the case of an unfollow app -- your friends list. According to the Facebook spokesperson, if you are using a third-party app that does not ask you for permission to use that information, it is probably not authorized by Facebook and might not be secure.
If you suspect an app is dicey, you can easily delete it
Accidentally download an app that you think might be shady? You can easily ditch it. Simply go into your Facebook settings, click “Apps” (which will be in the left column) and click the “X” by the app that you are ready to unfriend.