Two Headers

Obviously this only solves the code injection, not how it got there – so make sure to update wordpress and change all of your passwords.

But First follow All these resources:
http://codex.ww.wp.xz.cn/FAQ_My_site_was_hacked
http://ww.wp.xz.cn/support/topic/268083#post-1065779
http://smackdown.blogsblogsblogs.com/2008/06/24/how-to-completely-clean-your-hacked-wordpress-installation/
http://ottopress.com/2009/hacked-wordpress-backdoors/