diff --git a/anymail/webhooks/base.py b/anymail/webhooks/base.py
index 1f98bc66..c54bfc96 100644
--- a/anymail/webhooks/base.py
+++ b/anymail/webhooks/base.py
@@ -3,6 +3,7 @@
 
 import six
 from django.http import HttpResponse
+from django.utils.crypto import constant_time_compare
 from django.utils.decorators import method_decorator
 from django.views.decorators.csrf import csrf_exempt
 from django.views.generic import View
@@ -41,8 +42,13 @@ def __init__(self, **kwargs):
     def validate_request(self, request):
         """If configured for webhook basic auth, validate request has correct auth."""
         if self.basic_auth:
-            basic_auth = get_request_basic_auth(request)
-            if basic_auth is None or basic_auth not in self.basic_auth:
+            request_auth = get_request_basic_auth(request)
+            # Use constant_time_compare to avoid timing attack on basic auth. (It's OK that any()
+            # can terminate early: we're not trying to protect how many auth strings are allowed,
+            # just the contents of each individual auth string.)
+            auth_ok = any(constant_time_compare(request_auth, allowed_auth)
+                          for allowed_auth in self.basic_auth)
+            if not auth_ok:
                 # noinspection PyUnresolvedReferences
                 raise AnymailWebhookValidationFailure(
                     "Missing or invalid basic auth in Anymail %s webhook" % self.esp_name)
@@ -78,8 +84,11 @@ def validate_request(self, request):
         *All* definitions of this method in the class chain (including mixins)
         will be called. There is no need to chain to the superclass.
         (See self.run_validators and collect_all_methods.)
+
+        Security note: use django.utils.crypto.constant_time_compare for string
+        comparisons, to avoid exposing your validation to a timing attack.
         """
-        # if request.POST['signature'] != expected_signature:
+        # if not constant_time_compare(request.POST['signature'], expected_signature):
         #     raise AnymailWebhookValidationFailure("...message...")
         # (else just do nothing)
         pass