Date: Fri, 16 Jan 2015 13:16:17 +0100
From: Vulnerability Lab <research@...nerability-lab.com>
To: fulldisclosure@...lists.org
Subject: [FD] Facebook Bug Bounty #19 - Filter Bypass Web Vulnerability

Document Title:
===============
Facebook Bug Bounty #19 - Filter Bypass Web Vulnerability


References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=1381

Facebook Security ID: 221374210

Vulnerability Magazine: http://magazine.vulnerability-db.com/?q=articles/2015/01/14/facebook-bug-bounty-restriction-filter-bypass-vulnerability-id-221374210


Release Date:
=============
2015-01-14


Vulnerability Laboratory ID (VL-ID):
====================================
1381


Common Vulnerability Scoring System:
====================================
3.5


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:
==============================
The independent Vulnerability Laboratory Researcher Paulos Yibelo discovered a limitation bypass vulnerability in the official Mobile Site and mobile app (android/ios).


Vulnerability Disclosure Timeline:
==================================
2014-12-10: Researcher Notification & Coordination (Benjamin Kunz Mejri - Evolution Security)
2014-12-11: Vendor Notification (Facebook Security Team - Bug Bounty Program)
2014-12-15: Vendor Response/Feedback (Facebook Security Team - Bug Bounty Program)
2015-01-12: Vendor Fix/Patch (Facebook Developer Team - Reward: Bug Bounty)
2015-01-14: Public Disclosure (Vulnerability Laboratory)


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


Affected Product(s):
====================

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


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


Technical Details & Description:
================================
A restriction/limitation bypass web vulnerability has been discovered in the official Facebook Mobile web-application framework.

Facebook limits a name change for 60 days before a new name is applied. The advisory explains how i was able to bypass the restriction 
to change my `Alternative name` using parameter session tampering.

First the attacker uses a restricted account (60 day) and review the changes by using a session tamper. By a permanent exchange of the 
name values the service updates the name value through the mobile service without usage of the secure restriction mechanism. Remote attackers 
are able to bypass the restriction to exploit the vulnerability. The attack vector of the issue is location on the application-side and the 
request method to inject is POST.

Using this bug, a local attacker (a logged in user) can impersonate other users to manipulate their friends and change back to 
their account name (bypassing the 60day restriction).

The security risk of the filter bypass vulnerability is estimated as high with a cvss (common vulnerability scoring system) count of 3.5. 
Exploitation of the filter mechanism vulnerability requires a low privileged web-application user account without user interaction. 
Successful exploitation of the bypass issue results in unauthorized account name changes through alternative name inputs.

Request Method(s):
				[+] POST

Vulnerable Service(s):
				[+] Facebook - Mobile Website
				[+] Facebook Apps - Apple iOS & Android

Vulnerable Module(s):
				[+] ./settings/account/


Vulnerable Parameter(s):
				[+] name


Proof of Concept (PoC):
=======================
The bypass vulnerability can be exploited by remote attackers with a restricted user account and without user interaction.
For security demonstration or to reproduce the security vulnerability follow the provided information and steps below to continue.

Requirements: Attacker needs an account that changed its name and is limited for 60 (x) days before making any other changes

Manual steps to reproduce the vulnerability ...
1. Go to https://m.facebook.com/settings/account/?name&refid=70
2. Click review changes and tamper the request, change the value of
alternative name to anything
3. Continue the request and save the changed value
4. Submit request, then enter your test account password
5. Name value is changed even if time restriction was set
Note: Alternative name shall then be updated too
6. Facebook vulnerability successful exploited!

Reference(s):
https://m.facebook.com/settings/account/?name&refid=70


Security Risk:
==============
The security risk of the restriction/limitation bypass vulnerability in the change name function is estimated as medium. (CVSS 3.5)


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


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