Foreign javascript included on forumhome when referer is Google
 

Whenever I Google my site and click through, there is a script present in the markup that I don't recognize immediately after

HTML Code:

I checked the headlinclude template, and there is nothing about the foreign script in there after

Code:

In fact, I added some html comments immediately after the vbulletin_menu.js include in the headlinclude template, and the unrecognized JavaScript include gets inserted between the vbulletin_menu.js include and my html comment. That leads me to believe that something is doing a find and replace to include the unrecognized javascript in the output of the headlinclude template immediately after the vbulletin_menu.js include.

I have tried disabling plugins by adding

PHP Code:
define('DISABLE_HOOKS', true);

to config.php and it is still happening when I click a Google link to the site such that Google is the referer. :( I tried clearing the datastore and that did not cause it to go away, either.

I've grepped php files for any mention of "base64", "eval", etc. but can't find anything that looks suspicious.

Does anyone have any ideas?