[FD] CSRF/XSS vulnerability in Private Only could allow an attacker to do almost anything an admin user can (WordPress plugin)

[dxw Security <security@xxxxxxx>]

Details
================
Software: Private Only
Version: 3.5.1
Homepage: http://wordpress.org/plugins/private-only/
Advisory report: 
https://security.dxw.com/advisories/csrfxss-vulnerability-in-private-only-could-allow-an-attacker-to-do-almost-anything-an-admin-user-can/
CVE: CVE-2015-5483
CVSS: 5.8 (Medium; AV:N/AC:M/Au:N/C:P/I:P/A:N)

Description
================
CSRF/XSS vulnerability in Private Only could allow an attacker to do almost 
anything an admin user can

Vulnerability
================
This plugin fails to use CSRF and XSS prevention techniques which are available 
in WordPress (nonces, and esc_attr()) so it allows an attacker to cause a 
logged in admin user to be the victim of a CSRF attack which stores malicious 
content in the database which, due to lack of escaping, is output as raw HTML. 
Via JavaScript the attacker is able to cause the user’s browser to do almost 
anything including add users, delete posts, and even modify PHP files if that 
option hasn’t been disabled.

Proof of concept
================
Pressing the submit button here will change the logo setting to contain some 
JavaScript. Browsers with no reflected XSS prevention (like Firefox) will 
execute the JavaScript immediately, other browsers will execute the JavaScript 
when the page is loaded next.
<form method=\"POST\" 
action=\"http://localhost/wp-admin/options-general.php?page=privateonly.php\";>
  <input type=\"text\" name=\"po_logo\" 
value=\"&quot;>&lt;script>alert(1)&lt;/script>\">
  <input type=\"text\" name=\"po_submit\" value=\"Y\">
  <input type=\"submit\">
</form>

Mitigations
================

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
================

2015-03-20: Discovered
2015-07-09: Reported to vendor by email
2015-07-09: Requested CVE
2015-07-31: No reply. Tried on twitter and got a brief response
2015-08-18: After multiple further attempts, still no reply. Escalating to WP 
Plugins



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


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