Examine source code of Trail is Fun

{
  "theme": {
    "images": {
      "theme_frame": "header2.jpg"
    },
    "colors": {
      "frame": "#c9c9c9",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Trail is Fun",
  "manifest_version": 2,
  "description": "Frise humoristique sur le trail issue du site <a href=\"https://outgoing.prod.mozaws.net/v1/ef760b3dd6748d6cdb6879851b98389b96945069bdea2355e1f15714cb491cf4/http%3A//www.trail-nord.fr\" rel=\"nofollow\">www.trail-nord.fr</a>"
}