Featured image show the wrong image.

Hi

I was using facebook send button plugin to post to profile and groups (https://developers.facebook.com/docs/plugins/send-button). But the plugin picking the wrong featured image.

For example, I set the first image of this blog post (http://vitamin.ibucergas.com/kebaikan-polyphenol-dan-vivix/) as featured image. But the image that being used is randomly taken from my blog. And everytime I’m sharing other blog post the same random image will be shown.

May I know what’s actually the problem?