Trustwave SpiderLabs Security Advisory TWSL2021-018:
Authenticated Stored XSS in WordPress Plugin Age Gate

Published: 10/06/2021 
Version: 1.0

Vendor: Phil Baker (https://agegate.io/)
Product: WordPress Plugin Age Gate
Version affected:  <= 2.16.3

Product description:
The plugin provides functionality to affirm a user's age prior to viewing content.

Finding 1: Authenticated Stored XSS
*****Credit: Martin Vierula of Trustwave 
CWE: CWE-79

In the 'Messaging' page, the field 'Additional content' is vulnerable to stored XSS.  Scripts entered using this parameter will run against any web site visitor who is presented with the age check.

The plugin, in its 'Access' page, provides settings to select which WordPress roles have update authority on the 'Messaging' page, including the vulnerable field.  While 'Administrator' is the default, some web sites may have chosen to allow update access to lower-authority roles like Contributor or even Subscriber.

As a PoC, the following text can be entered directly into the 'Additional content' field in the browser:

</p><script>alert(123);</script><p>

Remediation Steps:
Upgrade the WordPress Plugin Age Gate to 2.16.4 or the latest stable version.

Revision History:
07/08/2021 - Vulnerability disclosed to vendor
07/09/2021 - Vendor releases version 2.16.3 with incomplete fix
07/13/2021 - Vendor releases version 2.16.4
10/06/2021 - Advisory published


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About Trustwave SpiderLabs:
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incident investigations, thousands of penetration tests and hundreds of
application security tests globally. In addition, the SpiderLabs Research
team provides intelligence through bleeding-edge research and proof of
concept tool development to enhance Trustwave's products and services.
https://www.trustwave.com/spiderlabs

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