Merge pull request jupyter#5898 from minrk/allow_origin_wildcard

handle allow_origin='*' in check_referer

Author: kevin-bates

notebook/base/handlers.py

@@ -404,6 +404,10 @@ def check_referer(self):
         Used on GET for api endpoints and /files/
         to block cross-site inclusion (XSSI).
         """
+
+        if self.allow_origin == "*" or self.skip_check_origin():
+            return True
+
         host = self.request.headers.get("Host")
         referer = self.request.headers.get("Referer")