I'm trying to display an Excel document from SharePoint2010 Excel Services in an iframe. But I'm getting an error due to the x-frame-options header. I have access to the to SharePoint server and all online searches tell me to go to IIS Manager -> HTTP Response Headers to remove it. But it's not there.
I tried adding my own header as suggested here: http://stackoverflow.com/questions/6666423/overcoming-display-forbidden-by-x-frame-options to no avail.
I also tried changing a SharePoint setting suggested here: Disabling X-FRAME-OPTION: SAMEORIGIN HTTP Response Header on SharePoint/PowerPivot xlsviewer.aspx. That didn't work either.
It's not a proxy adding it or anything because other SharePoint sites on the network do not have the header.
Is there another place x-frame-options could be set?
UPDATE: After more investigating, it turns out only the SharePoint Excel Services page (xlviewer.aspx) includes x-frame-options = SAMEORIGIN. So one would assume there's a setting in SharePoint.