[FD] 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@xxxxxxx>]

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@xxxxxxx to acknowledge this report if you 
received it via a third party (for example, plugins@xxxxxxxxxxxxx) 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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