Facebook leaks data (including private conversations) from 50 million accounts

40 million more “likely” affected

If you were born in the late 80s, you probably know the meaning of AFK. Otherwise, not only that you likely have no clue what it is, but chances are that you never logged out of your account. And that was perfectly fine.

Until today, when almost 90 million users have found themselves logged out of Facebook hours ago as a precaution to what appears to be the worst privacy blunder of the social network to date. And, yes, we’ve heard of Cambridge Analytica and the rest of the stories.

The story, frame by frame

As per Facebook’s announcement, almost 50 million accounts have been compromised through a daisy-chained vulnerability in the View As feature, which allowed an unknown party to snatch authentication tokens of these 50 million users. These authentication tokens allow you to stay logged into the account whenever you refresh the browser page, reboot the computer or put it to sleep. As long as you have the token, you are granted access to your account without having to actually go through the login process. Whoever has this token is also exempt from going through the login process, including whoever snatched it through this vulnerability.

There is little additional information about this bug, except for the fact that it has been partially mitigated by the social network disabling the View As feature, but it’s worth mentioning that there is no mention of a Bug Bounty reward or an account of a white-hat hacker reporting this vulnerability. At this point, it’s safe to assume that this was not a controlled report and that a third party literally walked away with at least 50 MILLION access tokens to as many accounts.

Here comes the painful part

According to Statista, Facebook Messenger is world’s second largest instant messaging platform with almost 1.3 billion active users. It’s also world’s largest instant messaging platform that does not have end-to-end encryption turned on by default. This means that chat history is always available from whatever machine you are logging into, unless you have manually turned on the Secret Conversations option. At this point, it’s safe to assume that, if you got logged out of Facebook for no apparent reason:

  1. Most likely your account was among the ones that have been hacked. Which brings us to point number 2.
  2. Your private posts, conversations and every piece of information, like check-ins, pictures sent via chat and so on, have likely fallen into the wrong hands. If, at any point, they become public following a “data dump”, marriages will get broken, friendship will end abruptly and sensitive pictures will flood the internet. Life will never be the same as before, “thanks” to a small bug in a platform.
  3. Other accounts using Facebook authentication might have been accessed.

As of now, it is hard to tell what hackers were able to get their hands on. However, given the complexity of the bug and the generous timeframe (the bug was caught last Tuesday by the social network, but it could have been exploited for way longer than this), it is fair to assume the worst. The reason you had to login again today was Facebook’s way of denying hackers access to the accounts: they invalidated the access token of both the 50M confirmed compromised accounts as well as the 40M accounts suspected of being compromised.

And, as we’re talking about extremely sensitive content such as private chat conversations, group chats and business-to-consumer interactions, changing your password won’t be enough to make everything OK again. So, if you’ve had sensitive content shared on the Facebook Messenger, it’s time to come to terms with it. If you’re a company that uses Facebook Messenger for support purposes and you’ve been logged out of your account, you’d better start evaluating what information has been exchanged across the medium and start notifying customers. This is by all account a data breach that falls under the GDPR and should be treated as such.

What you should do now

Today’s disclosure goes along the lines of the old adage saying “never put your eggs in one basket”. Social networks have become the centerpiece of our digital life that blurs into the physical life itself. It is also an account that social networks can do so much more than influence your shopping behavior or steal an election: it can have serious consequences on your lifestyle based on private social interactions.

Unfortunately, what has been seen cannot be unseen and there is little you can do right now to change the course of things. What you should do though is consider your future options:

  1. Understand that social networks are not bulletproof places where your secrets are safe. Plan for the worst and act accordingly.
  2. Never put something in writing that you would not like to leak several years from now when the platform gets breached.
  3. Embrace end-to-end encryption like your life and your freedom depend on it. Sometimes it does.
  4. Use privacy-focused IM clients such as Signal for sensitive chats or any other business that should stay segregated from your physical persona.

*** This is a Security Bloggers Network syndicated blog from HOTforSecurity authored by Bogdan Botezatu. Read the original post at: