Retrieving valid photo URL from FB Graph API WITH an extension

Using Facebook API and the picture data returned has a valid URL for the photo but it has no extension. This is causing problems for my file upload. How do I append an extension to the FB Photo URL or retrieve a FB photo URL with an extension?

API call:

me?fields=picture
"picture": {
    "data": {
      "height": 50,
      "is_silhouette": false,
      "url": "https://platform-lookaside.fbsbx.com/platform/profilepic/?asid=[somedata]&height=50&width=50&ext=[somedata]&hash=[somedata]",
"width": 50
    }