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INTERNET SECURITY AUDITORS ALERT 2016-002
- Original release date: February 16, 2016
- Last revised:  February 16, 2016
- Discovered by: Fabián Cuchietti
- Severity: 6.1/10 (CVSSv3 Base Metrics)
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I. VULNERABILITY
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Stored XSS in Google Sites

II. BACKGROUND
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Google Sites is a structured wiki and Web page-creation tool offered by
Google as part of the Google Apps for Work productivity suite. The goal
of Google Sites is for anyone to be able to create a team-oriented site
where multiple people can collaborate and share files.

III. DESCRIPTION
-------------------------
It possible to bypass the restriction on JavaScript execution in Google
with article by embedding an <iframe> with a data and base64. The
persistent (or stored) XSS vulnerability is a more devastating variant
of a cross-site scripting flaw: it occurs when the data provided by the
attacker is saved by the server, and then permanently displayed on
"normal" pages returned to other users in the course of regular
browsing, without proper HTML escaping. The affected resource is
https://sites.google.com/isecauditorstest/ when you create/Edit a new
article.

IV. PROOF OF CONCEPT
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First XSS:

1) Go to: https://sites.google.com/
2) Create > Blank template > Site Name: > Create
3) Browse to the URL vulnerable:
https://sites.google.com/site/isecauditorstest/ (example)
4) Edit > HTML > here insert the following payload: "><iframe
src="data:text/html;base64,PHNjcmlwdD5hbGVydCgnWFNTJyk8L3NjcmlwdD4">
5) To update
6) PoC: https://sites.google.com/site/isecauditorstest/


Second XSS:

1) Browse to URL vulnerable:
https://sites.google.com/site/isecauditorstest/ (example)
2) Create Page
3) Assign a name to your site: > Select a template: File cabinet > Create
4) Add file > select our file * .swf >  Copy the link to "See"
5) PoC:
https://sites.google.com/site/isecauditorstest/test-xssed/isec_flashxss.swf?attredirects=0

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 
google email, user credentials, personal data, etc.

VI. SYSTEMS AFFECTED
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https://sites.google.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
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This vulnerability has been discovered by Fabián Cuchietti (ofcuchietti
(at) isecauditors (dot) com).

X. REVISION HISTORY
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February 16, 2016: Initial release


XI. DISCLOSURE TIMELINE
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December 13, 2015   Vulnerability acquired by Internet Security Auditors
December 13, 2015   Contact with Google Security Team
December 14, 2015   Vendor Response/Feedback
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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