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INTERNET SECURITY AUDITORS ALERT 2016-001
- Original release date: February 16, 2016
- Last revised:  February 16, 2016
- Discovered by: José Antonio Pérez Piedra
- Severity: 6.1/10 (CVSSv3 Base Metrics)
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I. VULNERABILITY
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Desk.com is affected by Reflected Cross-Site Scripting vulnerability

II. BACKGROUND
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Desk.com is a help desk solution which allows companies to handle both
traditional 1-to-1 communications as well as monitor and respond to
social media. It also provides email support system and knowledgebase.

III. DESCRIPTION
-------------------------
Desk.com is affected by Reflected Cross-Site Scripting vulnerability in
the email contact form. The vulnerable resource does not properly check
the type of the parameters passed to the application through GET
requests. It allows malicious users to bypass the sanitizer and execute
arbitrary HTML/script code in the context of the victim's browser.

IV. PROOF OF CONCEPT
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The affected resource is:
/customer/portal/emails/new
    
All GET parameters are affected by this vulnerability, for example:
email[body]
email[subject]
interaction[email]
interaction[name]

The application does not filter the parameters if they are passed as
nested arrays and reflects its content in the response.

Here is a PoC:        
/customer/portal/emails/new?email[body]=&email[subject][]=asd'><img
src=x onerror=prompt(1)>&interaction[email]=&interaction[name]=

V. BUSINESS IMPACT
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An attacker can execute arbitrary HTML or script code in a targeted
user's browser, this can leverage to steal sensitive information as user
credentials, personal data, etc.

VI. SYSTEMS AFFECTED
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www.desk.com

VII. SOLUTION
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This vulnerability have been corrected.

VIII. REFERENCES
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http://www.owasp.org/index.php/Cross-site_Scripting_(XSS)

See Proof of Concept of exploitation in our Youtube channel.

IX. CREDITS
-------------------------
This vulnerability has been discovered by José Antonio Pérez Piedra,
japerez (at) isecauditors (dot) com.

X. REVISION HISTORY
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February 16, 2016: Initial release

XI. DISCLOSURE TIMELINE
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November 4, 2015:  Vulnerability acquired by Internet Security Auditors
November 6, 2015   Contact with Desk.com Security Team
December 1, 2015:  Internet Security Auditors confirm that the bug have
bveen corrected.
February 16, 2016:  Advisory published.

XII. LEGAL NOTICES
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The information contained within this advisory is supplied "as-is" with
no warranties or guarantees of fitness of use or otherwise. Internet
Security Auditors accepts no responsibility for any damage caused by the
use or misuse of this information.

XIII. ABOUT
-------------------------
Internet Security Auditors is a Spain based leader in web application
testing, network security, penetration testing, security compliance
implementation and assessing. Our clients include some of the largest
companies in areas such as finance, telecommunications, insurance, ITC,
etc. We are vendor independent provider with a deep expertise since
2001. Our efforts in R&D include vulnerability research, open security
project collaboration and whitepapers, presentations and security events
participation and promotion. For further information regarding our
security services, contact us.

XIV. FOLLOW US
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