Many wordpress theme use a popular image re-sizing script called Timthumb (http://www.binarymoon.co.uk/projects/timthumb/). The script is used by countless sites and is quite popular in the WordPress themeing community. That being said, it was noted yesterday that a vulnerability exists within certain versions of the script (http://code.google.com/p/timthumb/issues/detail?id=212), and therefore this vulnerability may also exist in your theme (depending on when you last updated it).
While the author has provided a fix, if you are using themes from ElegantThemes it is highly recommended that you update all of your themes to their latest versions. The latest versions of their themes no longer utilize the timthumb script and therefore are not subject to this security hole.
Regardless of when you last updated your theme, I would strongly suggest that everyone update their themes to the latest version and insure that the timthumb.php file and your /cache folder have been removed. To update your theme and remove the file, simply delete your current theme via the Appearances > Themes section of the WordPress Dashboard. Then you can re-download the theme from the members area and re-upload it normally. Please have in mind that any of your custom coding will be lost.
The latest theme versions require that your thumbnail images be hosted on the same domain name where WordPress is installed. If you were previously using timthumb.php to allow external image source by editing the file’s $allowedSites array, then these thumbnails will no longer function.
If your theme has a heavy custom work on it’s file, then just open the timthumb.php file and locate the following code and replace it:
$allowedSites = array ( 'flickr.com', 'picasa.com', 'blogger.com', 'wordpress.com', 'img.youtube.com', 'upload.wikimedia.org', );
$allowedSites = array ();
This will remove the vulnerability issue, but please have in mind, that if you are using images from external site like flickr.com, or other site, those images will not work anymore. I guess it’s better to reedit some of you post that to have a security breech.
There is also the option of updating timthumb.php to the latest version if you still want to use it. You can download the latest source code for the script here. Or, you can considering editing your current timthumb.php file to remove the external source functionality that is the cause of the vulnerability. You can learn more in this post by VaultPress. However, I would recommend downloading the new version of the theme instead.
Before updating the theme, make sure that you are using the latest version of WordPress. I would also disable all of your plugins temporarily before doing any update to insure that no compatibility issues exist. Remember to always keep WordPress, your Themes and your Plugins up-to-date to help protect yourself against any vulnerabilities.
This security flaw also applies to all of your inactive themes as well. If you have any theme, even if it is inactive, that contains the timthumb.php file then you are potentially at risk. I would suggest deleting all of the themes that you are not using in addition to updating the ones that you are. This file is very common throughout all WordPress themes, not just Elegant Themes.