Facebook reveals friends list even when it’s set to private

Also, sophos.com revealed to facebook.com, through an iframe, that I went and read an article on sophos.com about a facebook.com's vulnerability.

It's long past time for Facebook to simply stop using the words "private" and "delete" on any of their pages, because they obviously don't mean it whenever they use them.

I once made a fake FB account for testing purposes. I used private browsing in order to avoid having to log out of my real FB account. The two accounts never became friends or shared anything. The fake account does not have friends at all. The email address can not be tracked to me as well.

Yet every week, this email account receives an email with friend suggestions. I know about 75% of those people. With some of them , I'm not even friends on FB with my real account.

I think Facebook should just stop playing games and state that nothing will be private with the exception of personal messages. At least then everyone will know what to expect.

I’ve discovered this exact vulnerability (it is really a vulnerability, since you even see friendships when both people have set their friends list to "only me") about a year ago and sent Facebook the description to their white hat program. Their response was more or less "won’t fix, no security issue". But it’s kind of funny to see a public blog post about this issue now, maybe this creates some pressure.

The friend list issue seems to be an always "won't fix". I'm pretty sure every few or so security researchers, testers reach this "vulnerability" in one method or another. I've gotten a similar response from the Security Team for trying to dig up friend lists. Maybe it helps maybe it doesn't. I've learned to accept the stance and move on with other security holes.

"A friend connection is two-way - you friend someone, then they approve the friend request. In essence, a friend connection means both "Philippe considers John a friend" and "John considers Philippe a friend". In other words, both people involved have some ownership over this claim - which means the privacy isn't always as simple as with other content."

"Let me use the third example in your screenshots to illustrate. Mark Zuckerberg's friend list is not public. But Greg Golkin's friend list is public - meaning if you pull up Greg's friends, you can see Mark in the list. You can also see Kevin Scott is in the list. Kevin's friend list isn't public... but Stuart Gillette's is, so you can see Kevin show up there. Consequently, using fb:degrees hasn't shown you any information you couldn't theoretically figure out by looking at public friend lists - it's just made it easier to find that info."

"Now I that at first glance this might appear to be inconsistent or a privacy violation. But remember what I said earlier about the two parties involved in a friendship connection. Essentially, you're free to hide the fact that you consider John a friend, but it's also John's choice to publicize that he counts you as a friend - and hiding connections he's publicized would essentially override his privacy wishes. In some cases, such as with fb:degrees, we show connections if they're visible to you on at least one side of the friendship."

"Now, if Mark's list is private and all of his friends set their lists to private too, you should never get a result using fb:degrees. In that case, any final link in the chain connecting you to Mark would involve a friendship that was hidden to you from both sides of the connection, so we wouldn't display it to you."

"A common case where we get similar reports is the "friendship page" between two people - we show mutual friends of the two people if each of the two friend connections is visible to you on at least one side, but we hide any mutual friends where one of the connections is hidden on both sides. To help clarify some of these situations, we added this description to the friend list privacy setting: "Remember: Your friends control who can see their friendships on their own timelines. If people can see your friendship on another timeline, they'll be able to see it in news feed, search and other places on Facebook. They'll also be able to see mutual friends on your timeline."

This is a case where privacy can get complicated, but we think the way we've chosen to operate is a good balance of the competing priorities involved. We've also chosen to focus more on privacy controls around your content and personal information, since trying to maintain privacy by limiting discoverability is often an illusion. Since Facebook is a network designed for social participation, it's nearly impossible for it to work properly and let people stay completely hidden - there are many ways to discover a profile or friendship beyond friend lists or searches. But even if someone discovers your profile, you have a great degree of control about what they can then access.

I hope that helps clarify what you were observing here. Emrakul was also correct that we have rate limiting to prevent brute-forcing at scale, and given the above controls, even building up a list through iterations would never allow you to know for sure if you'd acquired the entire hidden friend list. I think our current setup is working as intended here, but definitely let us know if you think the controls I described can be overridden somehow."

You can also view a list of someone's friends by trying to recover their password. I reported it to their security team months ago and didn't get a response.

I reported this bug two weeks ago and they have not responded. This is the second time I've submitted a security bug and got nothing back...

I think you just have to accept that facebook, in general, has a 'share to a wide audience' as a default design stance. That stances enhances general viriality and usage of their program and thus increases their user base.

Same with never deleting anything, recording everything you do with like buttons around the internet and making it difficult to do such things as 'delete everything older than 3 months' with one click. Storage is cheap and the more information they have, the more valuable their product is to their customers, marketing firms.

Have a locked down by default stance just decreases the virality of their social product. The amount they piss off is smaller than the amount they gain unfortunately.

The article mentions the NSA, but if you don't think this can be used by anyone (not just people with huge botnets or databases like the NSA) then you'd be wrong as well. Consider trying to find the address of a person that you only know the facebook account of, but their name isn't listed in the phonebook. If you can see their friends list then it's fairly likely that it might have familiy members or housemates on it who _are_ listed. This is just one way of using the friends list. So it's a huge privacy issue that someone's friends list is exposed because anyone can use that information to figure out things about the person.

FB should've really kept the initial idea of a public worldwide friend-graph and build a special website for people who want to hang out in private (or let someone else build it).

I have a pseudonymous Facebook account that I use to access two private groups. My friends list is empty, which is nice. (It would be nicer if I didn't have an account and the people in the two private groups would check their email as often as they check Facebook so that we could use mailing lists instead of Facebook groups.)

Maybe Sophos should spend more time fixing their lousy software instead? As for security, you won't find it on FB.

The same is true for the profile picture which is always public even if you set the privacy settings to 'only me'. Opening the thumbnail in the browser and changing the image size in the URL lets you view a full size image. Wonder why they even give you the privacy option there.

So is this why I get random spam for which the name on the from address matches various Facebook friends?

In other news, clear incentive structures predict the future actions of companies.

FB makes money when they receive data created when people interact. Anything that limits this interaction, will eventually disappear. Take this reasoning to the limit, and everything will be made public.

1) Create a completely new zero account with no connections.

2) Send a friend request to a user whose "private" friends you want to see.

3) Immediately withdraw your friend request.

4) See the "people you might know" list, voilà.

(at least it used to work for me about a year ago when i was looking for one girl)

The article concludes with:

> I agree with Abezgauz on this issue: Facebook has no right to siphon our friends off of a list putatively set to be private.

Now it strikes me that Facebook does have that right. You gave them that right when you chose to create an account with them and chose to make friend connections with that account. If you don't like the way they operate, don't use their service. You'd have to live in a vacuum not to know that Facebook has been consistently pushing the envelope of acceptable privacy for years. The reality is that if you truly need complete privacy, a Facebook account is not for you.

Silly article. Why should Facebook fix anything here? Facebook is making billions of dollars the way it is. Facebook is a social networking site, not a private networking site. No one will get a reply to this because it's pointless. What you're asking for goes against the whole point of Facebook. Move on.

I think you can do it even without creating a fake account. The "People you may know" page seems to comprehensively list all of your friends' friends. All you'd need is some scraper software to build it into a better organised list.

man this privacy thing is a one nasty can of worms. they should've either kept it completely private or just public.

frankly if you are an extremely private person you shouldn't be using 'the facebook' but use email instead. few of my friends do just that.

regardless i think this is non-news-worthy article, facebook had this thing for a while and everyone here knows about that IMO.

my 2c

They trust me.