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Cross-Site Scripting in Magic Fields 1 WordPress Plugin
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Burak Kelebek, July 2016

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Abstract
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A reflected Cross-Site Scripting vulnerability has been encountered in
the Magic Fields 1 WordPress plugin. This issue allows an attacker to
perform a wide variety of actions, such as stealing Administrators'
session tokens, or performing arbitrary actions on their behalf.

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OVE ID
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OVE-20160724-0019

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Tested versions
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This issue was successfully tested on Magic Fields 1 version 1.7.1.

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Fix
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This issue is addressed in the 1.7.2 version of Magic Fields 1. You can
obtain the most recent version on the following location:
https://github.com/hunk/Magic-Fields/releases

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Details
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https://sumofpwn.nl/advisory/2016/cross_site_scripting_in_magic_fields_1_wordpress_plugin.html

Cross-Site Scripting (XSS) attacks are a type of injection, in which malicious scripts are injected into otherwise benign and trusted websites. XSS attacks occur when an attacker uses a web application to send malicious code, generally in the form of a browser script, to a different end user. Flaws that allow these attacks to succeed are quite widespread and occur when a web application uses input from a user without validating or encoding it. Reflected XSS occurs when user input is immediately returned by a web application in an error message, search result, or any other response that includes some or all of the input provided by the user as part of the request.

The plugin has several instances where XSS is possible due to lacking output encoding and user input sanitization:
1. The custom-write-panel-id field does not validate <script> tags and does not perform output encoding. Proof of concept code that demonstrates this issue is listed in the proof of concept section.
2. The value of the custom-group-id parameter in the RCCWP_CreateCustomFieldPage.php file is insufficiently validated:

53: echo $_GET['custom-group-id'];

3. The value of the custom-field-css parameter in the RCCWP_CreateCustomFieldPage.php file is insufficiently validated:

53: echo $_POST['custom-field-css'];

Proof of concept

Proof of concept code that demonstrates the Cross-Site Scripting in the custom-write-panel-id field is listed below:
http://<targetsite>/wp-admin/admin.php?page=MagicFieldsMenu&custom-write-panel-id=1" /><script>alert(1)</script>&mf_action=finish-create-custom-field


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