diff --git a/django/views/debug.py b/django/views/debug.py
index 6a0f81876ea..ffb343f12ba 100644
--- a/django/views/debug.py
+++ b/django/views/debug.py
@@ -11,6 +11,7 @@ from django.http import (HttpResponse, HttpResponseServerError,
     HttpResponseNotFound, HttpRequest, build_request_repr)
 from django.template import Template, Context, TemplateDoesNotExist
 from django.template.defaultfilters import force_escape, pprint
+from django.utils.datastructures import MultiValueDict
 from django.utils.html import escape
 from django.utils.encoding import force_bytes, smart_text
 from django.utils.module_loading import import_by_path
@@ -118,6 +119,20 @@ class SafeExceptionReporterFilter(ExceptionReporterFilter):
         """
         return settings.DEBUG is False
 
+    def get_cleansed_multivaluedict(self, request, multivaluedict):
+        """
+        Replaces the keys in a MultiValueDict marked as sensitive with stars.
+        This mitigates leaking sensitive POST parameters if something like
+        request.POST['nonexistent_key'] throws an exception (#21098).
+        """
+        sensitive_post_parameters = getattr(request, 'sensitive_post_parameters', [])
+        if self.is_active(request) and sensitive_post_parameters:
+            multivaluedict = multivaluedict.copy()
+            for param in sensitive_post_parameters:
+                if param in multivaluedict:
+                    multivaluedict[param] = CLEANSED_SUBSTITUTE
+        return multivaluedict
+
     def get_post_parameters(self, request):
         """
         Replaces the values of POST parameters marked as sensitive with
@@ -143,6 +158,15 @@ class SafeExceptionReporterFilter(ExceptionReporterFilter):
             else:
                 return request.POST
 
+    def cleanse_special_types(self, request, value):
+        if isinstance(value, HttpRequest):
+            # Cleanse the request's POST parameters.
+            value = self.get_request_repr(value)
+        elif isinstance(value, MultiValueDict):
+            # Cleanse MultiValueDicts (request.POST is the one we usually care about)
+            value = self.get_cleansed_multivaluedict(request, value)
+        return value
+
     def get_traceback_frame_variables(self, request, tb_frame):
         """
         Replaces the values of variables marked as sensitive with
@@ -173,17 +197,14 @@ class SafeExceptionReporterFilter(ExceptionReporterFilter):
                 for name, value in tb_frame.f_locals.items():
                     if name in sensitive_variables:
                         value = CLEANSED_SUBSTITUTE
-                    elif isinstance(value, HttpRequest):
-                        # Cleanse the request's POST parameters.
-                        value = self.get_request_repr(value)
+                    else:
+                        value = self.cleanse_special_types(request, value)
                     cleansed[name] = value
         else:
-            # Potentially cleanse only the request if it's one of the frame variables.
+            # Potentially cleanse the request and any MultiValueDicts if they
+            # are one of the frame variables.
             for name, value in tb_frame.f_locals.items():
-                if isinstance(value, HttpRequest):
-                    # Cleanse the request's POST parameters.
-                    value = self.get_request_repr(value)
-                cleansed[name] = value
+                cleansed[name] = self.cleanse_special_types(request, value)
 
         if (tb_frame.f_code.co_name == 'sensitive_variables_wrapper'
             and 'sensitive_variables_wrapper' in tb_frame.f_locals):
diff --git a/tests/view_tests/tests/test_debug.py b/tests/view_tests/tests/test_debug.py
index 618e2175a5c..c29b5520d57 100644
--- a/tests/view_tests/tests/test_debug.py
+++ b/tests/view_tests/tests/test_debug.py
@@ -24,7 +24,8 @@ from django.views.debug import ExceptionReporter
 from .. import BrokenException, except_args
 from ..views import (sensitive_view, non_sensitive_view, paranoid_view,
     custom_exception_reporter_filter_view, sensitive_method_view,
-    sensitive_args_function_caller, sensitive_kwargs_function_caller)
+    sensitive_args_function_caller, sensitive_kwargs_function_caller,
+    multivalue_dict_key_error)
 
 
 @override_settings(DEBUG=True, TEMPLATE_DEBUG=True)
@@ -511,6 +512,19 @@ class ExceptionReporterFilterTests(TestCase, ExceptionReportTestMixin):
             self.verify_paranoid_response(paranoid_view)
             self.verify_paranoid_email(paranoid_view)
 
+    def test_multivalue_dict_key_error(self):
+        """
+        #21098 -- Ensure that sensitive POST parameters cannot be seen in the
+        error reports for if request.POST['nonexistent_key'] throws an error.
+        """
+        with self.settings(DEBUG=True):
+            self.verify_unsafe_response(multivalue_dict_key_error)
+            self.verify_unsafe_email(multivalue_dict_key_error)
+
+        with self.settings(DEBUG=False):
+            self.verify_safe_response(multivalue_dict_key_error)
+            self.verify_safe_email(multivalue_dict_key_error)
+
     def test_custom_exception_reporter_filter(self):
         """
         Ensure that it's possible to assign an exception reporter filter to
diff --git a/tests/view_tests/views.py b/tests/view_tests/views.py
index 814931a717a..6e8fa7f8134 100644
--- a/tests/view_tests/views.py
+++ b/tests/view_tests/views.py
@@ -289,3 +289,16 @@ class Klass(object):
 
 def sensitive_method_view(request):
     return Klass().method(request)
+
+
+@sensitive_variables('sauce')
+@sensitive_post_parameters('bacon-key', 'sausage-key')
+def multivalue_dict_key_error(request):
+    cooked_eggs = ''.join(['s', 'c', 'r', 'a', 'm', 'b', 'l', 'e', 'd'])
+    sauce = ''.join(['w', 'o', 'r', 'c', 'e', 's', 't', 'e', 'r', 's', 'h', 'i', 'r', 'e'])
+    try:
+        request.POST['bar']
+    except Exception:
+        exc_info = sys.exc_info()
+        send_log(request, exc_info)
+        return technical_500_response(request, *exc_info)