A security issue and a vulnerability have been reported in WordPress, which can be exploited by malicious users to conduct script insertion attacks and compromise a vulnerable system.

1) The security issue is caused due to the wp_check_filetype() function in /wp-includes/functions.php improperly validating uploaded files. This can be exploited to execute arbitrary PHP code by uploading a malicious PHP script with multiple extensions.

Successful exploitation of this vulnerability requires that Apache is not configured to handle the mime-type for media files with an e.g. "gif", "jpg", "png", "tif", "wmv" extension.

2) Input passed via certain parameters to press-this.php is not properly sanitised before being displayed to the user. This can be exploited to insert arbitrary HTML and script code, which will be executed in a user's browser session in context of an affected site when the malicious data is being viewed.

The security issue and the vulnerability are reported in version 2.8.5. Other versions may also be affected.

Solution
Update to version 2.8.6.

Provided and/or discovered by
1) Dawid Golunski
2) The vendor credits Benjamin Flesch.

Changelog
Further details available to Secunia VIM customers

Original Advisory
http://wordpress.org/development/2009/11/wordpress-2-8-6-security-release/

Deep Links
Links available to Secunia VIM customers