At first glance, the "thisisyourdigitallife" Facebook quiz looked like any other. If you wanted to take part you just had to download the app, log in via Facebook, agree to share some profile information, and that was it.
And around 270,000 people did just that.
But the app actually did a lot more. It is now at the centre of a huge scandal involving a British data firm linked to Donald Trump's presidential campaign and the UK's Brexit Leave campaign.
Because what users may not have known is that along with their own data, they were also allowing the app to access their friends' information, and it's this extension of the data harvesting – and what was done with it – that has made headlines.
It is thought that the information of around 50 million people was harvested using the app, and used to influence politics in the US and the UK.
On Sunday a whistleblower called Christopher Wylie claimed most of this personal information had been taken without authorisation. He said Cambridge Analytica had used it to build a powerful software program to predict and influence choices at the ballot box.
Not only would this be in violation of Facebook's guidelines on how to use that data – but it also begs the question of whether or not users knew this was possible in the first place.
Cambridge Analytica has now been suspended by Facebook following these allegations.
Rachel Neaman, head of the not-for-profit Corsham Institute which looks to empower people when using technology, said there is a lack of understanding of how this data can be used to target users with adverts or other content.
"What people may not realise is that they're being targeted with other forms of content too, like articles, surveys, imagery that again reinforces what is already their opinion, already their world view and already their filter bubble and that in itself is highly concerning," Neaman added.
However, you can make some meaningful changes to your Facebook settings to stop the network sharing your data with apps.
Here's how:
1. Head to Settings. This can be found in the top right-hand corner of Facebook's profile page. Once within the settings menu head to the bottom left-hand corner of the screen and you'll see the word Apps.
Once you click on this you'll see every external app, or internal app, that uses Facebook either as a login or as a third-party service.
You'll know and recognise some of them, for example Instagram, Bitmoji or Fitbit, but you might also notice a few that you don't – maybe you did a quiz when you were younger or logged into an app on your phone that you deleted soon after.
Click on any app and you'll see exactly how much information about you this app has access to.
For example, "Cities I've Visited" was a simple map app I downloaded years ago to help track my holidays and share them with my friends. Yet when I look at what information I've shared with them, it's almost everything including my birthday, education history, work history, current location, all photos including any that I'm tagged in and of course, my likes.
How to stop your friends sharing your data to apps
Your friends can also share your data with any apps that they sign up to, too.
This depends on your wider visibility settings, so the information they can share with apps is only the information that you then let your friends see.
To prevent this, head to the same App section of the Settings menu, and scroll down until you see Apps others use.
Click on Edit and you'll see a dizzying array of tick boxes which let you decide what information you share with your friends and the apps that they use.
You can untick every single one of these boxes if you want to, but the only way to truly stop any public information being shared is to disable Platform Apps entirely.
Of course, if you do that you then won't have access to any app that requires a Facebook login.
To do this, head to the App section of the Settings menu and scroll down until you see Apps, Websites and Plug-ins.
Click Edit and you'll be given the option to turn every app off and disable all app access to your Facebook data.
How to control what data you share with advertisers and others
While what we've just discussed can help you control what information you're sharing through apps it's not the full picture.
To get a complete understanding of how your Facebook information is being shared to advertisers head to Settings and then Ads.
From there you'll be able to see why certain adverts are being shared to you and also control the amount of data that they can receive.
Finally to then control the amount of information you share with other people on Facebook head to Settings and then Privacy.
