Insecure ssl elements

Once installed, the dashboard page url displays a triangle warning of insecure content. The same behaviour is shown on the plugin configuration page.

The images that cause this behavior are:
http://cdn.wpbeginner.com/pluginimages/wpbeginner.gif
http://cdn.wpbeginner.com/pluginimages/feed.png
http://cdn.wpbeginner.com/pluginimages/email.gif
http://cdn.wpbeginner.com/pluginimages/facebook.png

Could you use protocol relative urls and allow ssl connections to cdn.wpbeginner.com?

Nowadays ssl connections don’t have a noticeable impact on performance if the server is properly configured.

https://wordpress.org/plugins/insert-headers-and-footers/