Mixed content warnings on HTTPS website

My website is running under HTTPS, but Chrome tells me the site is not fully secure, and in the developers console I get mixed content warnings. The problem is due to how this plugin loads code from addthis.com.

See my comment on another support request for details: https://ww.wp.xz.cn/support/topic/ssl-support-for-the-addthis-widget/#post-8945738

The fix on your part is incredibly simple — just change http://... links to simply //