Yahoo! Bug Bounty #25 Flickr API - Persistent Vulnerability

Type vulnerlab
Reporter Vulnerability Laboratory [Research Team] - Ateeq ur Rehman Khan ( []
Modified 2014-07-06T00:00:00


                                            Document Title:
Yahoo! Bug Bounty #25 Flickr API - Persistent Vulnerability

References (Source):

Release Date:

Vulnerability Laboratory ID (VL-ID):

Common Vulnerability Scoring System:

Product & Service Introduction:
Flickr is an image hosting and video hosting website, and web services suite that was created by Ludicorp in 2004 and acquired by Yahoo 2005. 
In addition to being a popular website for users to share and embed personal photographs, and effectively an online community, the service is 
widely used by photo researchers and by bloggers to host images that they embed in blogs and social media.

The Verge reported in March 2013 that Flickr had a total of 87 million registered members and more than 3.5 million new images uploaded daily.
In August 2011 the site reported that it was hosting more than 6 billion images and this number continues to grow steadily according to 
reporting sources. Photos and videos can be accessed from Flickr without the need to register an account but an account must be made in order 
to upload content onto the website. Registering an account also allows users to create a profile page containing photos and videos that the 
user has uploaded and also grants the ability to add another Flickr user as a contact. For mobile users, Flickr has official mobile apps for 
iOS, Android, PlayStation Vita, and Windows Phone operating systems.

(Copy of the Homepage: )

Abstract Advisory Information:
The Vulnerability Laboratory Research team discovered a persistent input validation web vulnerability in the official Yahoo Flickr! website web-application and api.

Vulnerability Disclosure Timeline:
2013-11-03:	Researcher Notification & Coordination (Ateeq ur Rehman Khan - Vulnerability Lab)
2013-11-04:	Vendor Notification (Yahoo! Security Team - Bug Bounty Program)
2014-01-09:	Vendor Response/Feedback (Yahoo! Security Team - Bug Bounty Program)
2014-06-22:	Vendor Fix/Patch (Yahoo! Developer Team - HackerOne Reward: 1000$)
2014-07-06:	Public Disclosure (Vulnerability Laboratory)

Discovery Status:

Affected Product(s):
Product: Flickr Web Application - YPL API  2013 Q3

Exploitation Technique:

Severity Level:

Technical Details & Description:
A persistent input validation vulnerability has been discovered in the official Yahoo Flickr! website web-application and api.
The vulnerability allows remote attackers to inject own malicious script codes on the application-side of the online-service.

The vulnerability is located in the flickr `invite` mail notification module. Remote attackers are able to inject payloads to 
the `message` value of the web-application notification service after the registration. The remote attacker can send invitation 
mails through the yahoo online-service module with manipulated message body context. The attack vector of the issue is located 
on the application-side and the request method to inject own malicious codes is POST.

The security risk of the persistent remote web vulnerability is estimated as medium with a cvss (common vulnerability scoring 
system) count of 4.1. Exploitation of the vulnerability requires low user interaction and a low privileged flickr web-application 
user account. Successful exploitation of the vulnerability result in session hijacking (customers), account steal via persistent 
web attack (mail), persistent phishing or persistent manipulation of notification mails module context.

Vulnerable Service(s):
				[+] Yahoo! > Flickr

Vulnerable Module(s):
				[+] Invite (Invitation of Users)

Vulnerable Module(s):
				[+] Notification Service (eMails)

Vulnerable Parameter(s):
				[+] message (body)

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

PoC: Flickr Message - Invitation Attachment > Message Body

    <tr style="mso-yfti-irow:1">
      <td style="padding:1.5pt 1.5pt 1.5pt 1.5pt">
      <p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif""> <o:p></o:p></span></p>
     <tr style="mso-yfti-irow:2">
      <td style="border:solid #CCCCCC 1.0pt;mso-border-alt:solid #CCCCCC .75pt;
      padding:7.5pt 7.5pt 7.5pt 7.5pt">
      <p class="MsoNormal" style="line-height:13.5pt"><span style="font-size:
      10.0pt;font-family:"Arial","sans-serif"">I want to share my Flickr
      photostream with you. If you get bored of that, there's loads of other
      things to see there too. '%3d[PERSISTENT INJECTED SCRIPT CODE VIA MESSAGE VALUE!!!]'>"><b><span style="color:#E83DA6">free</span></b>
      and takes less than a minute with your Yahoo! ID.<o:p></o:p></span></p>

Note: pTest:>


Solution - Fix & Patch:
The vulnerability can be patched by a secure parse and encode of the vulnerable message body value input.
Filter or encode also the outgoing mails with the vulnerable db stored message body context to prevent script cod executions.

Security Risk:
The security risk of the persistent input validation web vulnerability is estimated as medium(+).

Credits & Authors:
Vulnerability Laboratory [Research Team] - Ateeq ur Rehman Khan ( []

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