fix bug in example

Author: FilipStamenkovic

prebid/native-implementation.md

@@ -469,13 +469,13 @@ window.renderAd=function(ortb){
             return asset.video.vasttag;
         }
     }
-    
+
     ortb.assets.forEach(asset => {
         template = template.replace(`##hb_native_asset_id_${asset.id}##`, getAssetValue(asset));
     });
-    
+
     if (ortb.privacy) {
-        template = template.replace("hb_native_privacy", ortb.privacy);
+        template = template.replace("##hb_native_privacy##", ortb.privacy);
     }
     template = template.replace("##hb_native_linkurl##", ortb.link.url);
 	return template;
@@ -564,7 +564,7 @@ window.renderAd = (ortb) => {
             };
 
             let message = JSON.stringify(viewabilityRecord);
-            window.parent.postMessage(JSON.stringify(message), '*');
+            window.parent.postMessage(message, '*');
         })
     }