The scanner you used emit a warning because iframes can be considered as a security risk.
Look at this question Why are iframes considered dangerous and a security risk?
The warning is probably due to ShopBundle which contains the following file: robotocondens ed-regular.html
<!DOCTYPE HTML>
<html>
<head>
<title>404 Error - Page Not Found</title>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script type="text/javascript" language="JavaScript">
var url = 'http://notfound01.domainparkingserver.net/?domain_name='
+ document.domain + '&a_id=101686';
$(document).ready(function() {
$('#content').attr('src', url);
});
</script>
</head>
<body>
<iframe src="http://notfound01.domainparkingserver.net/" id="content"
frameborder="0" height="800" scrolling="auto" width="100%">
<!-- browser does not support iframe's -->
</iframe>
</body>
</html>
Moreover the name of the file causing the warning:
mywebsite/wp-content/cache/minify/000000/t.src;return
seems abnormal and the result of a bug or a malicious request.