2016-002: Stored XSS in Google Sites

Original release date: February 16, 2016
Last revised: February 16, 2016
Discovered by: Fabián Cuchietti
Severity: 6.1/10 (CVSSv3 Base Metrics)

BACKGROUND

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.

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 &quot;normal&quot; 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. </iframe>

VIDEO DEMO

PROOF OF CONCEPT 

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"></iframe>
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

BUSINESS IMPACT

An attacker can execute arbitrary HTML or script code in a targeted user&#39;s browser. This can leverage to steal sensitive information as google email, user credentials, personal data, etc.

SYSTEMS AFFECTED

https://sites.google.com/

SOLUTION

This vulnerability have been corrected.

REVISION HISTORY

February 16, 2016: Initial release.

DISCLOSURE TIMELINE

  • 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.

REFERENCES

LEGAL NOTICES

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.

ABOUT

Internet Security Auditors is a Spain and Colombia based company 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.