Date: Thu, 25 Dec 2014 10:54:38 +0100
From: Vulnerability Lab <research@...nerability-lab.com>
To: bugtraq@...urityfocus.com, bugs@...uritytracker.com
Subject: Facebook Bug Bounty #17 - Migrate Privacy Vulnerability

Document Title:
===============
Facebook Bug Bounty #17 - Migrate Privacy Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=1370

Facebook Security ID: 216850649

Vulnerability Magazine: http://magazine.vulnerability-db.com/?q=articles/2014/12/23/facebook-social-network-privacy-issue-disclosed-bug-bounty-program-whitehat


Release Date:
=============
2014-12-23


Vulnerability Laboratory ID (VL-ID):
====================================
1370


Common Vulnerability Scoring System:
====================================
4.9


Product & Service Introduction:
===============================
Facebook is an online social networking service, whose name stems from the colloquial name for the book given to students 
at the start of the academic year by some university administrations in the United States to help students get to know 
each other. It was founded in February 2004 by Mark Zuckerberg with his college roommates and fellow Harvard University 
students Eduardo Saverin, Andrew McCollum, Dustin Moskovitz and Chris Hughes. The website`s membership was initially limited 
by the founders to Harvard students, but was expanded to other colleges in the Boston area, the Ivy League, and Stanford University. 
It gradually added support for students at various other universities before opening to high school students, and eventually to anyone 
aged 13 and over. Facebook now allows any users who declare themselves to be at least 13 years old to become registered users of the site.

Users must register before using the site, after which they may create a personal profile, add other users as friends, and exchange messages, 
including automatic notifications when they update their profile. Additionally, users may join common-interest user groups, organized by workplace, 
school or college, or other characteristics, and categorize their friends into lists such as `People From Work` or `Close Friends`. As of 
September 2012, Facebook has over one billion active users, of which 8.7% are fake. According to a May 2011 Consumer Reports survey, there are 
7.5 million children under 13 with accounts and 5 million under 10, violating the site`s terms of service.

In May 2005, Accel partners invested $12.7 million in Facebook, and Jim Breyer added $1 million of his own money to the pot. A January 2009 
Compete.com study ranked Facebook as the most used social networking service by worldwide monthly active users. Entertainment Weekly included the 
site on its end-of-the-decade `best-of` list, saying, `How on earth did we stalk our exes, remember our co-workers` birthdays, bug our friends, 
and play a rousing game of Scrabulous before Facebook?` Facebook eventually filed for an initial public offering on February 1, 2012, and was 
headquartered in Menlo Park, California. Facebook Inc. began selling stock to the public and trading on the NASDAQ on May 18, 2012. Based on its 
2012 income of USD 5.1 Billion, Facebook joined the Fortune 500 list for the first time, being placed at position of 462 on the list published in 2013.

(Copy of the Homepage: http://en.wikipedia.org/wiki/Facebook )


Abstract Advisory Information:
==============================
An Indepnedent Vulnerability Laboratory Researcher discovered a privacy vulnerability in the official Facebook Social Network mobile web-application.


Vulnerability Disclosure Timeline:
==================================
2014-10-31: Researcher Notification & Coordination (Paulos Yibelo)
2014-11-01: Vendor Notification (Facebook Security Team - Bug Bounty Program)
2014-11-07: Vendor Response/Feedback (Facebook Security Team - Bug Bounty Program)
2014-11-13: Vendor Fix/Patch (Facebook Developer Team - Bug Bounty: 2500$)
2014-11-15: Second Report
2014-12-13: Vendor Fix/Patch (Facebook Developer Team)
2014-12-19: Bug Bounty Payment (Facebook Security Team - Bug Bounty Program)
2014-12-23: Public Disclosure (Vulnerability Laboratory)


Discovery Status:
=================
Published


Affected Product(s):
====================
Facebook
Product: Mobile Web Application (API) 2014 Q4


Exploitation Technique:
=======================
Remote


Severity Level:
===============
Medium


Technical Details & Description:
================================
A privacy vulnerability has been discovered in the official Facebook Social Network mobile web-application.
The security vulnerability allows to bypass the privacy security settings to access restricted web context.

There is an indirect object reference bug (which they already been notified by someone other than me,) that allows users who convert
their accounts to a page using (https://www.facebook.com/pages/create.php?migrate) access everything by requesting mobile based url`s 
like m.facebook.com/messages/nofications which stores everything their account had and facebook said was removed.

so, using that bug, accessing user`s profile is easy, for example, Himanshu Sharma  account converted into a page`s url is 
https://m.facebook.com/xxx.net (from the mobile interface) simply by requesting his url (since he liked my page), or atleast was my 
friend while I change my account at page - I will be able to see his shares for his privacy setting stating only `Friends`.

The second logic flaw (currently 0day) is, after the first bug fix (privacy?) settings. but now a new flaw seemed to be made, this one
however is a little more practically unsafe and you didn`t notice because it only not affects the people who view my profile`s setting
but those that are friends with them and arent included with my page.

Request Method(s):
			[+] POST

Vulnerable Module(s):
			[+] create.php?migrate

Affected Module(s):
			[+] Friend Share - Privacy Settings


Proof of Concept (PoC):
=======================
The privacy issue can be exploited by remote attackers with low privileged application user account with low user interaction.
For security demonstration or to reproduce the security vulnerability follow the provided information and steps below to continue.

Case of Scenario: Privacy Settings
Lets say for example I was friends with X before my account was a page, say Y is friends with X but Y isn't my friend. now I change 
my account to a page, which essentially forces X to like my page. Now while all this happening, Y have no idea. but when Y shares 
something with the privacy setting "Friends of Friends", I shall be able to see his shares just because X was my friend in the 
conversion process so Y is my "friend of friends".


Solution - Fix & Patch:
=======================
2014-12-22: Vendor Fix/Patch (Facebook Developer Team)


Security Risk:
==============
The security risk of the privacy vulnerability in the facebook mobile social network is estimated as medium. (CVSS 4.9)


Credits & Authors:
==================
Paulos Yibelo (paulosyibelo.com)


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=========================
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