V14 upgrade with iframe was not loading in HTTPS

Experience Manager (PaaS/OnPrem)
1

After V14 upgrade CMS pages iframe was not loading over https and throws below error in browser console.

iframe request returns 302 redirect

Error:
Mixed Content: The page at ‘https://site.io/cms’ was loaded over HTTPS, but requested an insecure frame ‘http://site.io/cms/?1&iframe’. This request has been blocked; the content must be served over HTTPS.

2

browsers started blocking mixed content (http over https). you need to either serve all your content/resources from httpS to fix it for all users or temporary disable this error in your browser setting for individuals