There is a WordPress worm that adds malicious (more or less) code to all functions.php files on the server (either online or offline/local). Here’s my StackExchange question, still working on finding an automated way of removing it.http://wordpress.stackexchange.com/questions/74367/how-to-remove-the-automated-code-posted-in-functions-php
UPDATE AND SOLUTION :
Clean all the malicious code (see my PasteBin link above) from all functions.php files (best to check globally using a text editor like Notepad++) and you’re done. Check all downloaded themes for the code in functions.php file. There are more themes infected with this code online.