Images replaced with code

I’m currently working on a WordPress site that appears to have been compromised. The content of several images have been replaced with the same code for an HTML page including javascript with an iframe having the source of “content.incapsula.com/jsTest.html”

However, I haven’t been able to find any malicious code or suspicious files on the site otherwise. I’ve even ran several security scans from various plugins and they all return clean.