wordpress-logoIf you’re running a WordPress blog on your servers that isn’t version 2.8.4  you’re strongly advised to upgrade immediately to the latest version of the software to avoid an ongoing attack. WordPress.com hosted blogs are not affected.

The issue was first reported by Lorelle on WordPress after it was discovered that an attack is exploiting security holes in previous versions, creating a hidden Admin account and drilling right down to the database level.

Lorelle writes:

There are two clues that your WordPress site has been attacked. There are strange additions to the pretty permalinks, such as example.com/category/post-title/%&(%7B$%7Beval(base64_decode($_SERVER%5BHTTP_REFERER%5D))%7D%7D|.+)&%/. The keywords are “eval” and “base64_decode.”

The second clue is that a “back door” was created by a “hidden” Administrator. Check your site users for “Administrator (2)” or a name you do not recognize. You will probably be unable to access that account.

All Wordpress users are advised to upgrade to the latest version of WP (2.8.4). Those already affected will likely need to export all content with the built-in XML WordPress exporting utility, uninstall and reinstall WordPress and re-import the content.