Nessus report shows a medium level issue that "Web Application Potentially Vulnerable to Clickjacking" with the description as follows:
"The remote web server does not set an X-Frame-Options response header in all content responses. This could potentially expose the site to a clickjacking or UI Redress attack wherein an attacker can trick a user into clicking an area of the vulnerable page that is different than what the user perceives the page to be. This can result in a user performing fraudulent or malicious transactions"
We could add X-Frame-Options, supported in all major browsers, in the Http response header to mitigate the issue.