diff --git index.php index.php
index 40a6fbe..2e1117a 100644
--- index.php
+++ index.php
@@ -2087,10 +2087,14 @@ function computeThumbnail($url,$href=false)
             $path = parse_url($url,PHP_URL_PATH);
             if ("/talks/" !== substr($path,0,7)) return array(); // This is not a single video URL.
         }
+    }
         $sign = hash_hmac('sha256', $url, $GLOBALS['salt']); // We use the salt to sign data (it's random, secret, and specific to each installation)
+        $thumbname=hash('sha1',$url).'.gif';
+        $filepath=$GLOBALS['config']['CACHEDIR'].'/'.$thumbname;
+        if (sha1_file($filepath) != '48d45d7ada69f9f858849bbd6e459f66c9694ee7')
+
         return array('src'=>index_url($_SERVER).'?do=genthumbnail&hmac='.$sign.'&url='.urlencode($url),
                      'href'=>$href,'width'=>'120','style'=>'height:auto;','alt'=>'thumbnail');
-    }
 
     // For all other, we try to make a thumbnail of links ending with .jpg/jpeg/png/gif
     // Technically speaking, we should download ALL links and check their Content-Type to see if they are images.
@@ -2400,18 +2404,30 @@ function genThumbnail()
     else
     {
         // For all other domains, we try to download the image and make a thumbnail.
-        // We allow 30 seconds max to download (and downloads are limited to 4 Mb)
-        list($headers, $data) = get_http_url($url, 30);
-        if (strpos($headers[0], '200 OK') !== false) {
-            $filepath=$GLOBALS['config']['CACHEDIR'].'/'.$thumbname;
-            file_put_contents($filepath,$data); // Save image to cache.
-            if (resizeImage($filepath))
-            {
-                header('Content-Type: image/jpeg');
-                echo file_get_contents($filepath);
-                return;
-            }
-        }
+        list($httpstatus,$headers,$data) = get_http_url($url,30);  // We allow 30 seconds max to download (and downloads are limited to 4 Mb)
+        // Extract the link to the thumbnail
+        $doc = new DOMDocument();
+        libxml_use_internal_errors(true);
+        $doc->loadHTML($data);
+        foreach( $doc->getElementsByTagName('meta') as $meta )
+                if ($meta->getAttribute('property') == 'og:image')
+                    $imageurl=$meta->getAttribute('content');
+        if (!empty($imageurl))
+        {   // Let's download the image.
+                list($httpstatus,$headers,$data) = get_http_url($imageurl,20); // No control on image size, so wait long enough.
+                if (strpos($httpstatus,'200 OK')!==false)
+                {
+                    $filepath=$GLOBALS['config']['CACHEDIR'].'/'.$thumbname;
+                    file_put_contents($filepath,$data); // Save image to cache.
+                    if (resizeImage($filepath))
+                    {
+                        header('Content-Type: image/jpeg');
+                        echo file_get_contents($filepath);
+                        return;
+                    }
+                }
+         }
+
     }