It seems that the plugin call an external link to generate the frame content:
https://s9e.github.io/iframe/2/facebook.min.html#{@type}{@id} (Git) then this page call the us version of Facebook components: //connect.facebook.net/en_US/sdk.js#xfbml=1&version=v2.5
I found it in CachedDefinitionCollection.php:
'facebook'=>[
'attributes'=>[],
'example'=>[
'https://www.facebook.com/FacebookDevelopers/posts/10151471074398553',
'https://www.facebook.com/video/video.php?v=10150451523596807',
'https://www.facebook.com/photo.php?fbid=10152476416772631',
'https://www.facebook.com/ign/videos/10153762113196633/',
'https://www.facebook.com/southamptonfc/videos/vb.220396037973624/1357764664236750/'
],
'extract'=>[
'@/(?!(?:apps|developers|graph)\\.)[-\\w.]*facebook\\.com/(?:[/\\w]+/permalink|(?!pages/|groups/).*?)(?:/|fbid=|\\?v=)(?\'id\'\\d+)(?=$|[/?&#])@',
'@facebook\\.com/(?\'user\'\\w+)/(?\'type\'post|video)s?/@',
'@facebook\\.com/video/(?\'type\'post|video)\\.php@'
],
'homepage'=>'https://www.facebook.com/',
'host'=>['facebook.com'],
'iframe'=>[
'data-s9e-livepreview-ignore-attrs'=>'style',
'onload'=>'var c=new MessageChannel;c.port1.onmessage=function(e){{style.height=e.data+\'px\'}};contentWindow.postMessage(\'s9e:init\',\'https://s9e.github.io\',[c.port2])',
'src'=>'https://s9e.github.io/iframe/2/facebook.min.html#{@type}{@id}'
],
'name'=>'Facebook',
'scrape'=>[],
'tags'=>['social']
],
The fact is that this page is common for all those who use the plugin, may be i can try to create my own iframe page and change link in CachedDefinitionCollection.php
The only evolution i can see is to deploy frame pages on the package instead of a public website, it will be more customizable but maybe it's like that for a specific reason i don't know.