Enforce https for githubusercontent.com

app/config/config_prod.yml

@@ -95,7 +95,7 @@ nelmio_security:
             img-src:
                 - 'self'
                 - 'https://www.gravatar.com/'
-                - '*.githubusercontent.com'
+                - 'https://*.githubusercontent.com'
                 - 'https://raw.github.com/'
                 - 'https://github.com/'
                 - 'https://gitlab.com/'