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Subject: [FD] Bugcrowd Bug Bounty #7 - Persistent Web Vulnerability
From: Vulnerability Lab <research () vulnerability-lab ! com>
Date: 2016-05-25 9:24:45
Message-ID: 6c16a518-3802-43f1-7de3-02f1fa97ab79 () vulnerability-lab ! com
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Document Title:
===============
Bugcrowd Bug Bounty #7 - Persistent Web Vulnerability
References (Source):
====================
http://www.vulnerability-lab.com/get_content.php?id=1830
ID: b40f63ed19074014df808599e44684f6a18bb6f4f51cf21948ef78df2f56c13b
Release Date:
=============
2016-05-10
Vulnerability Laboratory ID (VL-ID):
====================================
1830
Common Vulnerability Scoring System:
====================================
3.8
Product & Service Introduction:
===============================
From the outback to the valley, Bugcrowd is paving the way for crowdsourced security. Founded \
in 2012 in Australia by Casey Ellis, Bugcrowd is now based in San Francisco and is backed by \
Costanoa Venture Capital, Rally Ventures, Paladin Capital Group and Blackbird Ventures.
(Copy of the Homepage: https://bugcrowd.com/about )
Abstract Advisory Information:
==============================
The vulnerability laboratory research team discovered an application-side vulnerability in the \
official Bugcrowd online service web-application.
Vulnerability Disclosure Timeline:
==================================
2016-04-20: Researcher Notification & Coordination (Benjamin Kunz Mejri - Evolution Security \
GmbH)
2016-04-21: Vendor Notification (Bugcrowd - Bug Bounty Program)
2016-**-**: Vendor Fix/Patch (Bugcrowd - Bug Bounty Program)
2016-05-03: Acknowledgement & Bug Bounty (Bugcrowd - Bug Bounty Program)
2016-05-10: Public Disclosure (Vulnerability Laboratory)
Discovery Status:
=================
Published
Affected Product(s):
====================
Bugcrowd
Product: Online Service - Web Application 2016 Q2
Exploitation Technique:
=======================
Remote
Severity Level:
===============
Medium
Technical Details & Description:
================================
A persistent script code injection and application-side mail encode web vulnerability has been \
discovered in the official Bugcrowd online service web-application. The vulnerability typ \
allows an attacker to inject own malicious script code to the application-side of the \
vulnerable service function or web modules context.
The bugcrowd service allows to register by a web formular in the webpage to receive new \
information like "... Bugcrowd`s Next Chapter". In the name values attackers are able to \
inject malicious script codes. In an advisory send to bugcrowd about 1 year ago we already \
mentioned the problem but your team was not able to verify the bug finally. Thus time we \
exploited the bug by using casey ellis wrong encoded context of the bugcrowd registered users \
to stream the code with the service emails. The injection point is the formular registration \
for receiving information of bugcrowd and the execution point is the email body context with \
the broken encode values. The code directly executes after the arrival in the main body \
context and the sender of the email was the mail support@bugcrowd inbox.
The security risk of the application-side cross site web vulnerability is estimated as medium \
with a cvss (common vulnerability scoring system) count of 3.7. Exploitation of the persistent \
input validation web vulnerability requires a low privileged web-application user account and \
low or medium user interaction. Successful exploitation of the vulnerability results in \
session hijacking, persistent phishing attacks, persistent external redirects to malicious \
source and persistent manipulation of affected or connected application modules.
Request Method(s):
[+] POST
Vulnerable Parameter(s):
[+] Firstname
[+] Lastname
[+] Companyname
Affected Module(s):
[+] Email Community Letter - (community@bugcrowd.com)
Proof of Concept (PoC):
=======================
The security vulnerability can be exploited by remote attackers without user interaction or \
privileged web-application user account. For security demonstration or to reproduce the \
vulnerability follow the provided information and steps below to continue.
PoC: Email: We've raised money, here's what's next from Bugcrowd (community@bugcrowd.com) - \
Casey Ellis <p style="margin-bottom: 1em; -webkit-text-size-adjust:100%;
-ms-text-size-adjust:100%">Hi "><[PERSISTENT INJECTED SCRIPT CODE EXECUTION!]")" \
<="" "="">&lt;iframe src=a onload=alert("PENTEST") &lt;,&lt;/p&gt; &lt;p \
style="margin-bottom: 1em; -webkit-text-size-adjust:100%; -ms-text-size-adjust:100%"&gt;As \
you may have&amp;nbsp;already heard, this morning we &lt;a \
href="https://bugcrowd.com/resources/bugcrowd-15-million-raises-series-b" \
style="-webkit-text-size-adjust:100%; -ms-text-size-adjust:100%" \
data-hs-link-id="0"&gt;announced our $15M Series B funding&lt;/a&gt;. We're proud \
to have many of our previous investors joining us again, as well as pleased to welcome new \
investors to the family. &lt;br&gt;&lt;br&gt;We couldn't have done this without \
you. With your help we've built a massive&amp;nbsp;community of hackers, made up of diverse \
and talented folks from all over the world.&lt;br&gt;&lt;br&gt;We've got lots \
of plans for what's next and I've shared those details on our blog. Please check it out to \
learn more.&lt;br&gt;&lt;br&gt;&lt;strong&gt;&lt;a \
href="https://blog.bugcrowd.com/15-million-to-connect-hackers-and-companies-bugcrowd-series-b" \
style="-webkit-text-size-adjust:100%; -ms-text-size-adjust:100%" \
data-hs-link-id="1"&gt;Read about our plans for Bugcrowd's next \
chapter&lt;/a&gt;.&lt;/strong&gt; &lt;/p&gt;&lt;p \
style="margin-bottom: 1em; -webkit-text-size-adjust:100%; \
-ms-text-size-adjust:100%"&gt;Thank you joining us on this journey. There's so much more to \
come! We hope you'll &lt;a href="https://twitter.com/Bugcrowd/status/722904657366884353" \
style="-webkit-text-size-adjust:100%; -ms-text-size-adjust:100%" \
data-hs-link-id="0"&gt;join us today in our celebration&lt;/a&gt; of this Bugcrowd \
community milestone.&lt;/p&gt; &lt;p style="margin-bottom: 1em; \
-webkit-text-size-adjust:100%; -ms-text-size-adjust:100%"&gt;Sincerely,&lt;/p&gt; \
&lt;p style="margin-bottom: 1em; -webkit-text-size-adjust:100%; \
-ms-text-size-adjust:100%"&gt;Casey Ellis&lt;br&gt;Bugcrowd Founder &amp;amp; \
CEO&lt;/p&gt;&lt;/div&gt;
Solution - Fix & Patch:
=======================
The vulnerability can be patched by a secure parse and encode of the vulnerable firstname, \
lastname and company values in the add POST method request. Disallow the usage of special chars \
in the name values, encode the inputs as well to prevent further exploitation. Encode as well \
outgoing emails to ensure that no malicious script code injection can take place with \
application-side attack vector.
Security Risk:
==============
The security risk of the filter bypass issue and application-side arbitrary script code \
injection web vulnerability is estimated as medium. (CVSS 3.8)
Credits & Authors:
==================
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri (research@vulnerability-lab.com) \
[www.vulnerability-lab.com] [http://www.vulnerability-lab.com/show.php?user=Benjamin%20K.M.]
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=========================
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