More disappointing news for fans of both social networks and privacy, two concepts which seem increasingly incompatible. Facebook has this week admitted to using phone numbers uploaded solely for security purposes as part of its ad targeting efforts.

Facebook has always been relatively open about its business model; it’s essentially a gigantic ad network, making billions per year by dumping commercials in front of its user’s eyeballs. In return, they get a free service. This is not astounding news, and plenty of other companies (cough, Google) use the same tactics. Fair enough.

But this latest admission, revealed by TechCrunch, goes a step further than just using the information you upload to your profile to target relevant ads. Apparently, it’s also using the phone numbers of people who only upload them for the purpose of securing their data with two-factor authentication. These numbers can be cross-referenced with the phone numbers from advertisers’ databases, meaning that if you gave your number to an online shop and then again to register for two-factor authentication with Facebook, the company can put two and two together to build a profile around your shopping habits.

As explained by a Facebook spokesperson: “We are clear about how we use the information we collect, including the contact information that people upload or add to their own accounts. You can manage and delete the contact information you’ve uploaded at any time.” The official response is that if you don’t like your number being used for marketing purposes, your only opt-out choice is to stop using the two-factor security system altogether. It doesn’t matter whether you share your details publicly to your profile or not.

We’ve never had to write so much news about Facebook in a single year, but as one of the biggest and most-used companies in the world we can’t just ignore these kinds of privacy violations. If you need reminding, read our recap on the Cambridge Analytica data harvesting scandal, or this data misuse story from last month – and if you feel like ditching the big F for good, see our guide to apps you can use to replace its core functions.