I'm working on a site for our local school and it's been hacked with hidden spam code. It shows up in the page's source code right above the wrapper and container divs. See http://www.miravistaschool.com. It's on every page or post.
I've checked the Header and Index files of my theme and see nothing out of sorts. I've also tried switching to the native 2012 theme and it still exists. I've also switched off all plugins and it didn't change anything.
I updated to v3.6 and that didn't change anything. I ran WordFence and it did not detect any file anomalies.
I've run through several hack cleanup tutorials and it looks like I've run through the checklist of standard things to do. Any other suggestions on locating the source file of the hack before I do a fresh file install? What really confuses me is that if it IS malicious code inside a file, wouldn't WordFence pick it up?