WordPress Plugin Resume Submissions & Job Postings 2.5.1 - Unrestricted Arbitrary File Upload

# Exploit Title: WordPress Resume Submissions & Job Postings v2.5.1 Unrestricted File Upload
# Date: 7/9/12
# Exploit Author: Chris Kellum
# Vendor Homepage: http://www.geerservices.com/
# Software Link: http://downloads.wordpress.org/plugin/resume-submissions-job-postings.2.5.1.zip
# Version: 2.5.1



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Vulnerability Details
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When submitting a resume, the "file attachment" upload does not restrict any file types.

Attachments are uploaded to the following folder:

/wp-content/uploads/rsjp/attachments/

File names are rewritten by the following code in lines 193-197 of /wp-content/plugins/resume-submissions-job-postings/includes/functions.php:

	foreach( $_FILES[$input]['error'] as $key => $error ){

		if ( $error == UPLOAD_ERR_OK ) {

			$tmpName  = $_FILES[$input]['tmp_name'][$key];

			$ext      = getExtension( $_FILES[$input]['name'][$key] );

			$name     = md5( date( 'Y-m-d H:i:s' ) ) . '-' . $count . '.' . $ext;

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Proof of Concept
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When submitting the resume form, attach a shell (c99.php, etc.) or file of your choice as a "file attachment."

After submitting the form, navigate to /wp-content/uploads/rsjp/attachments/ to find all uploaded attachments.

Locate your file by searching for the file extension (.php, etc.) or by file size.

Alternatively, your uploaded file can be accessed directly by understanding how the plugin renames files.

The plugin creates an MD5 hash of the server date and time, appends a hyphen and the number of the upload, followed by the file extension.

Example:

If server date and time is 2012-07-09 21:22:20 and only one file is attached, file name will be output as 813a2040e8ef7fe3661972696409b562-1.php, which can be located at /wp-content/uploads/rsjp/attachments/813a2040e8ef7fe3661972696409b562-1.php

To retrieve server date and time, use an intercepting proxy such as Burp Suite and check the history to locate the date/time that the server returned the 200 code after submitting the resume form.

In PoC, 1 second was added to the time in order to properly locate the uploaded file. If the 200 code was sent at 2012-07-09 21:22:19, MD5 encoding 2012-07-09 21:22:20 would create the proper file name.