diff --git a/Gemfile b/Gemfile
index 04c9f9808a74be28f8e8b99ff5c651386e0c1ddd..d3cd9fa7edac855eb1a8221f0677094dbb29a318 100644
--- a/Gemfile
+++ b/Gemfile
@@ -163,7 +163,7 @@ gem 'diffy', '~> 3.1.0'
 gem 'diff_match_patch', '~> 0.1.0'
 
 # Application server
-gem 'rack', '~> 2.0.7'
+gem 'rack', '~> 2.0.9'
 
 group :unicorn do
   gem 'unicorn', '~> 5.4.1'
diff --git a/Gemfile.lock b/Gemfile.lock
index 2ae0c014f22de8d2cf85b157419cbd0fff083238..36d7d68c33673eaf48141125b5020a01814b97ec 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -160,7 +160,7 @@ GEM
     concord (0.1.5)
       adamantium (~> 0.2.0)
       equalizer (~> 0.0.9)
-    concurrent-ruby (1.1.5)
+    concurrent-ruby (1.1.6)
     connection_pool (2.2.2)
     contracts (0.11.0)
     cork (0.3.0)
@@ -767,7 +767,7 @@ GEM
     public_suffix (4.0.3)
     pyu-ruby-sasl (0.0.3.3)
     raabro (1.1.6)
-    rack (2.0.7)
+    rack (2.0.9)
     rack-accept (0.4.5)
       rack (>= 0.4)
     rack-attack (6.2.0)
@@ -836,17 +836,17 @@ GEM
       json
     recursive-open-struct (1.1.0)
     redis (4.1.3)
-    redis-actionpack (5.1.0)
-      actionpack (>= 4.0, < 7)
-      redis-rack (>= 1, < 3)
+    redis-actionpack (5.2.0)
+      actionpack (>= 5, < 7)
+      redis-rack (>= 2.1.0, < 3)
       redis-store (>= 1.1.0, < 2)
     redis-activesupport (5.2.0)
       activesupport (>= 3, < 7)
       redis-store (>= 1.3, < 2)
     redis-namespace (1.6.0)
       redis (>= 3.0.4)
-    redis-rack (2.0.6)
-      rack (>= 1.5, < 3)
+    redis-rack (2.1.2)
+      rack (>= 2.0.8, < 3)
       redis-store (>= 1.2, < 2)
     redis-rails (5.0.2)
       redis-actionpack (>= 5.0, < 6)
@@ -1303,7 +1303,7 @@ DEPENDENCIES
   prometheus-client-mmap (~> 0.10.0)
   pry-byebug (~> 3.5.1)
   pry-rails (~> 0.3.4)
-  rack (~> 2.0.7)
+  rack (~> 2.0.9)
   rack-attack (~> 6.2.0)
   rack-cors (~> 1.0.0)
   rack-oauth2 (~> 1.9.3)
diff --git a/app/models/active_session.rb b/app/models/active_session.rb
index f37da1b7f59bafbf2c8671454cdb22ae7a8a4f42..050155398ab39b37e8001bc77c137b5ff0586a08 100644
--- a/app/models/active_session.rb
+++ b/app/models/active_session.rb
@@ -6,31 +6,32 @@ class ActiveSession
   SESSION_BATCH_SIZE = 200
   ALLOWED_NUMBER_OF_ACTIVE_SESSIONS = 100
 
-  attr_writer :session_id
-
   attr_accessor :created_at, :updated_at,
     :ip_address, :browser, :os,
     :device_name, :device_type,
-    :is_impersonated
+    :is_impersonated, :session_id
 
   def current?(session)
     return false if session_id.nil? || session.id.nil?
 
-    session_id == session.id
+    # Rack v2.0.8+ added private_id, which uses the hash of the
+    # public_id to avoid timing attacks.
+    session_id.private_id == session.id.private_id
   end
 
   def human_device_type
     device_type&.titleize
   end
 
+  # This is not the same as Rack::Session::SessionId#public_id, but we
+  # need to preserve this for backwards compatibility.
   def public_id
-    encrypted_id = Gitlab::CryptoHelper.aes256_gcm_encrypt(session_id)
-    CGI.escape(encrypted_id)
+    Gitlab::CryptoHelper.aes256_gcm_encrypt(session_id.public_id)
   end
 
   def self.set(user, request)
     Gitlab::Redis::SharedState.with do |redis|
-      session_id = request.session.id
+      session_id = request.session.id.public_id
       client = DeviceDetector.new(request.user_agent)
       timestamp = Time.current
 
@@ -63,32 +64,35 @@ class ActiveSession
 
   def self.list(user)
     Gitlab::Redis::SharedState.with do |redis|
-      cleaned_up_lookup_entries(redis, user).map do |entry|
-        # rubocop:disable Security/MarshalLoad
-        Marshal.load(entry)
-        # rubocop:enable Security/MarshalLoad
+      cleaned_up_lookup_entries(redis, user).map do |raw_session|
+        load_raw_session(raw_session)
       end
     end
   end
 
   def self.destroy(user, session_id)
+    return unless session_id
+
     Gitlab::Redis::SharedState.with do |redis|
       destroy_sessions(redis, user, [session_id])
     end
   end
 
   def self.destroy_with_public_id(user, public_id)
-    session_id = decrypt_public_id(public_id)
-    destroy(user, session_id) unless session_id.nil?
+    decrypted_id = decrypt_public_id(public_id)
+
+    return if decrypted_id.nil?
+
+    session_id = Rack::Session::SessionId.new(decrypted_id)
+    destroy(user, session_id)
   end
 
   def self.destroy_sessions(redis, user, session_ids)
-    key_names = session_ids.map {|session_id| key_name(user.id, session_id) }
-    session_names = session_ids.map {|session_id| "#{Gitlab::Redis::SharedState::SESSION_NAMESPACE}:#{session_id}" }
+    key_names = session_ids.map { |session_id| key_name(user.id, session_id.public_id) }
 
-    redis.srem(lookup_key_name(user.id), session_ids)
+    redis.srem(lookup_key_name(user.id), session_ids.map(&:public_id))
     redis.del(key_names)
-    redis.del(session_names)
+    redis.del(rack_session_keys(session_ids))
   end
 
   def self.cleanup(user)
@@ -110,28 +114,65 @@ class ActiveSession
     sessions_from_ids(session_ids_for_user(user.id))
   end
 
+  # Lists the relevant session IDs for the user.
+  #
+  # Returns an array of Rack::Session::SessionId objects
   def self.session_ids_for_user(user_id)
     Gitlab::Redis::SharedState.with do |redis|
-      redis.smembers(lookup_key_name(user_id))
+      session_ids = redis.smembers(lookup_key_name(user_id))
+      session_ids.map { |id| Rack::Session::SessionId.new(id) }
     end
   end
 
+  # Lists the ActiveSession objects for the given session IDs.
+  #
+  # session_ids - An array of Rack::Session::SessionId objects
+  #
+  # Returns an array of ActiveSession objects
   def self.sessions_from_ids(session_ids)
     return [] if session_ids.empty?
 
     Gitlab::Redis::SharedState.with do |redis|
-      session_keys = session_ids.map { |session_id| "#{Gitlab::Redis::SharedState::SESSION_NAMESPACE}:#{session_id}" }
+      session_keys = rack_session_keys(session_ids)
 
       session_keys.each_slice(SESSION_BATCH_SIZE).flat_map do |session_keys_batch|
         redis.mget(session_keys_batch).compact.map do |raw_session|
-          # rubocop:disable Security/MarshalLoad
-          Marshal.load(raw_session)
-          # rubocop:enable Security/MarshalLoad
+          load_raw_session(raw_session)
         end
       end
     end
   end
 
+  # Deserializes an ActiveSession object from Redis.
+  #
+  # raw_session - Raw bytes from Redis
+  #
+  # Returns an ActiveSession object
+  def self.load_raw_session(raw_session)
+    # rubocop:disable Security/MarshalLoad
+    session = Marshal.load(raw_session)
+    # rubocop:enable Security/MarshalLoad
+
+    # Older ActiveSession models serialize `session_id` as strings, To
+    # avoid breaking older sessions, we keep backwards compatibility
+    # with older Redis keys and initiate Rack::Session::SessionId here.
+    session.session_id = Rack::Session::SessionId.new(session.session_id) if session.try(:session_id).is_a?(String)
+    session
+  end
+
+  def self.rack_session_keys(session_ids)
+    session_ids.each_with_object([]) do |session_id, arr|
+      # This is a redis-rack implementation detail
+      # (https://github.com/redis-store/redis-rack/blob/master/lib/rack/session/redis.rb#L88)
+      #
+      # We need to delete session keys based on the legacy public key name
+      # and the newer private ID keys, but there's no well-defined interface
+      # so we have to do it directly.
+      arr << "#{Gitlab::Redis::SharedState::SESSION_NAMESPACE}:#{session_id.public_id}"
+      arr << "#{Gitlab::Redis::SharedState::SESSION_NAMESPACE}:#{session_id.private_id}"
+    end
+  end
+
   def self.raw_active_session_entries(redis, session_ids, user_id)
     return [] if session_ids.empty?
 
@@ -146,7 +187,7 @@ class ActiveSession
     entry_keys = raw_active_session_entries(redis, session_ids, user_id)
 
     entry_keys.compact.map do |raw_session|
-      Marshal.load(raw_session) # rubocop:disable Security/MarshalLoad
+      load_raw_session(raw_session)
     end
   end
 
@@ -159,10 +200,13 @@ class ActiveSession
     sessions = active_session_entries(session_ids, user.id, redis)
     sessions.sort_by! {|session| session.updated_at }.reverse!
     destroyable_sessions = sessions.drop(ALLOWED_NUMBER_OF_ACTIVE_SESSIONS)
-    destroyable_session_ids = destroyable_sessions.map { |session| session.send :session_id } # rubocop:disable GitlabSecurity/PublicSend
+    destroyable_session_ids = destroyable_sessions.map { |session| session.session_id }
     destroy_sessions(redis, user, destroyable_session_ids) if destroyable_session_ids.any?
   end
 
+  # Cleans up the lookup set by removing any session IDs that are no longer present.
+  #
+  # Returns an array of marshalled ActiveModel objects that are still active.
   def self.cleaned_up_lookup_entries(redis, user)
     session_ids = session_ids_for_user(user.id)
     entries = raw_active_session_entries(redis, session_ids, user.id)
@@ -181,13 +225,8 @@ class ActiveSession
   end
 
   private_class_method def self.decrypt_public_id(public_id)
-    decoded_id = CGI.unescape(public_id)
-    Gitlab::CryptoHelper.aes256_gcm_decrypt(decoded_id)
+    Gitlab::CryptoHelper.aes256_gcm_decrypt(public_id)
   rescue
     nil
   end
-
-  private
-
-  attr_reader :session_id
 end
diff --git a/app/services/groups/destroy_service.rb b/app/services/groups/destroy_service.rb
index c9c6b54a791d650a93ebec32dc1438a8d0d0339d..9437eb9eede691ffff9278656a88c001b605601d 100644
--- a/app/services/groups/destroy_service.rb
+++ b/app/services/groups/destroy_service.rb
@@ -29,7 +29,15 @@ module Groups
 
       group.chat_team&.remove_mattermost_team(current_user)
 
+      user_ids_for_project_authorizations_refresh = group.user_ids_for_project_authorizations
+
       group.destroy
+
+      UserProjectAccessChangedService
+        .new(user_ids_for_project_authorizations_refresh)
+        .execute(blocking: true)
+
+      group
     end
     # rubocop: enable CodeReuse/ActiveRecord
   end
diff --git a/changelogs/unreleased/213665-update_project_authorizations_on_group_delete.yml b/changelogs/unreleased/213665-update_project_authorizations_on_group_delete.yml
new file mode 100644
index 0000000000000000000000000000000000000000..8b7443f25ba1f028fa7cf298c807218d364acd67
--- /dev/null
+++ b/changelogs/unreleased/213665-update_project_authorizations_on_group_delete.yml
@@ -0,0 +1,5 @@
+---
+title: Refresh ProjectAuthorization during Group deletion
+merge_request:
+author:
+type: security
diff --git a/changelogs/unreleased/security-update-rack-2-0-9.yml b/changelogs/unreleased/security-update-rack-2-0-9.yml
new file mode 100644
index 0000000000000000000000000000000000000000..2dec5d2782ec76289f99fc1a7b92c7ec560d0dfa
--- /dev/null
+++ b/changelogs/unreleased/security-update-rack-2-0-9.yml
@@ -0,0 +1,5 @@
+---
+title: Update rack and related gems to 2.0.9 to fix security issue
+merge_request:
+author:
+type: security
diff --git a/db/post_migrate/20200204113225_schedule_recalculate_project_authorizations_third_run.rb b/db/post_migrate/20200204113225_schedule_recalculate_project_authorizations_third_run.rb
new file mode 100644
index 0000000000000000000000000000000000000000..47b22b4800aeaf24781c1f95c633d481990b1335
--- /dev/null
+++ b/db/post_migrate/20200204113225_schedule_recalculate_project_authorizations_third_run.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+class ScheduleRecalculateProjectAuthorizationsThirdRun < ActiveRecord::Migration[5.1]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  MIGRATION = 'RecalculateProjectAuthorizationsWithMinMaxUserId'
+  BATCH_SIZE = 2_500
+  DELAY_INTERVAL = 2.minutes.to_i
+
+  disable_ddl_transaction!
+
+  class User < ActiveRecord::Base
+    include ::EachBatch
+
+    self.table_name = 'users'
+  end
+
+  def up
+    say "Scheduling #{MIGRATION} jobs"
+
+    queue_background_migration_jobs_by_range_at_intervals(User, MIGRATION, DELAY_INTERVAL, batch_size: BATCH_SIZE)
+  end
+
+  def down
+  end
+end
diff --git a/spec/migrations/schedule_recalculate_project_authorizations_third_run_spec.rb b/spec/migrations/schedule_recalculate_project_authorizations_third_run_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..0ce8b020b914795d4a218901062689d522a151f5
--- /dev/null
+++ b/spec/migrations/schedule_recalculate_project_authorizations_third_run_spec.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20200204113225_schedule_recalculate_project_authorizations_third_run.rb')
+
+describe ScheduleRecalculateProjectAuthorizationsThirdRun, :migration, :sidekiq do
+  let(:users_table) { table(:users) }
+
+  before do
+    stub_const("#{described_class}::BATCH_SIZE", 2)
+
+    1.upto(4) do |i|
+      users_table.create!(id: i, name: "user#{i}", email: "user#{i}@example.com", projects_limit: 1)
+    end
+  end
+
+  it 'schedules background migration' do
+    Sidekiq::Testing.fake! do
+      Timecop.freeze do
+        migrate!
+
+        expect(BackgroundMigrationWorker.jobs.size).to eq(2)
+        expect(described_class::MIGRATION).to be_scheduled_migration(1, 2)
+        expect(described_class::MIGRATION).to be_scheduled_migration(3, 4)
+      end
+    end
+  end
+end
diff --git a/spec/models/active_session_spec.rb b/spec/models/active_session_spec.rb
index bff3ac313c4c5744d85f6d40d91dd11ed25d1591..d43c64f36f6a50ce931398cc67131c984328b5ae 100644
--- a/spec/models/active_session_spec.rb
+++ b/spec/models/active_session_spec.rb
@@ -9,10 +9,8 @@ RSpec.describe ActiveSession, :clean_gitlab_redis_shared_state do
     end
   end
 
-  let(:session) do
-    double(:session, { id: '6919a6f1bb119dd7396fadc38fd18d0d',
-                       '[]': {} })
-  end
+  let(:rack_session) { Rack::Session::SessionId.new('6919a6f1bb119dd7396fadc38fd18d0d') }
+  let(:session) { instance_double(ActionDispatch::Request::Session, id: rack_session, '[]': {}) }
 
   let(:request) do
     double(:request, {
@@ -25,13 +23,13 @@ RSpec.describe ActiveSession, :clean_gitlab_redis_shared_state do
 
   describe '#current?' do
     it 'returns true if the active session matches the current session' do
-      active_session = ActiveSession.new(session_id: '6919a6f1bb119dd7396fadc38fd18d0d')
+      active_session = ActiveSession.new(session_id: rack_session)
 
       expect(active_session.current?(session)).to be true
     end
 
     it 'returns false if the active session does not match the current session' do
-      active_session = ActiveSession.new(session_id: '59822c7d9fcdfa03725eff41782ad97d')
+      active_session = ActiveSession.new(session_id: Rack::Session::SessionId.new('59822c7d9fcdfa03725eff41782ad97d'))
 
       expect(active_session.current?(session)).to be false
     end
@@ -46,14 +44,12 @@ RSpec.describe ActiveSession, :clean_gitlab_redis_shared_state do
 
   describe '#public_id' do
     it 'returns an encrypted, url-encoded session id' do
-      original_session_id = "!*'();:@&\n=+$,/?%abcd#123[4567]8"
+      original_session_id = Rack::Session::SessionId.new("!*'();:@&\n=+$,/?%abcd#123[4567]8")
       active_session = ActiveSession.new(session_id: original_session_id)
-      encrypted_encoded_id = active_session.public_id
-
-      encrypted_id = CGI.unescape(encrypted_encoded_id)
+      encrypted_id = active_session.public_id
       derived_session_id = Gitlab::CryptoHelper.aes256_gcm_decrypt(encrypted_id)
 
-      expect(original_session_id).to eq derived_session_id
+      expect(original_session_id.public_id).to eq derived_session_id
     end
   end
 
@@ -104,7 +100,8 @@ RSpec.describe ActiveSession, :clean_gitlab_redis_shared_state do
   describe '.list_sessions' do
     it 'uses the ActiveSession lookup to return original sessions' do
       Gitlab::Redis::SharedState.with do |redis|
-        redis.set("session:gitlab:6919a6f1bb119dd7396fadc38fd18d0d", Marshal.dump({ _csrf_token: 'abcd' }))
+        # Emulate redis-rack: https://github.com/redis-store/redis-rack/blob/c75f7f1a6016ee224e2615017fbfee964f23a837/lib/rack/session/redis.rb#L88
+        redis.set("session:gitlab:#{rack_session.private_id}", Marshal.dump({ _csrf_token: 'abcd' }))
 
         redis.sadd(
           "session:lookup:user:gitlab:#{user.id}",
@@ -127,17 +124,18 @@ RSpec.describe ActiveSession, :clean_gitlab_redis_shared_state do
         redis.sadd("session:lookup:user:gitlab:#{user.id}", session_ids)
       end
 
-      expect(ActiveSession.session_ids_for_user(user.id)).to eq(session_ids)
+      expect(ActiveSession.session_ids_for_user(user.id).map(&:to_s)).to eq(session_ids)
     end
   end
 
   describe '.sessions_from_ids' do
     it 'uses the ActiveSession lookup to return original sessions' do
       Gitlab::Redis::SharedState.with do |redis|
-        redis.set("session:gitlab:6919a6f1bb119dd7396fadc38fd18d0d", Marshal.dump({ _csrf_token: 'abcd' }))
+        # Emulate redis-rack: https://github.com/redis-store/redis-rack/blob/c75f7f1a6016ee224e2615017fbfee964f23a837/lib/rack/session/redis.rb#L88
+        redis.set("session:gitlab:#{rack_session.private_id}", Marshal.dump({ _csrf_token: 'abcd' }))
       end
 
-      expect(ActiveSession.sessions_from_ids(['6919a6f1bb119dd7396fadc38fd18d0d'])).to eq [{ _csrf_token: 'abcd' }]
+      expect(ActiveSession.sessions_from_ids([rack_session])).to eq [{ _csrf_token: 'abcd' }]
     end
 
     it 'avoids a redis lookup for an empty array' do
@@ -152,11 +150,12 @@ RSpec.describe ActiveSession, :clean_gitlab_redis_shared_state do
       redis = double(:redis)
       expect(Gitlab::Redis::SharedState).to receive(:with).and_yield(redis)
 
-      sessions = %w[session-a session-b]
+      sessions = %w[session-a session-b session-c session-d]
       mget_responses = sessions.map { |session| [Marshal.dump(session)]}
-      expect(redis).to receive(:mget).twice.and_return(*mget_responses)
+      expect(redis).to receive(:mget).exactly(4).times.and_return(*mget_responses)
 
-      expect(ActiveSession.sessions_from_ids([1, 2])).to eql(sessions)
+      session_ids = [1, 2].map { |id| Rack::Session::SessionId.new(id.to_s) }
+      expect(ActiveSession.sessions_from_ids(session_ids).map(&:to_s)).to eql(sessions)
     end
   end
 
@@ -212,6 +211,12 @@ RSpec.describe ActiveSession, :clean_gitlab_redis_shared_state do
   end
 
   describe '.destroy' do
+    it 'gracefully handles a nil session ID' do
+      expect(described_class).not_to receive(:destroy_sessions)
+
+      ActiveSession.destroy(user, nil)
+    end
+
     it 'removes the entry associated with the currently killed user session' do
       Gitlab::Redis::SharedState.with do |redis|
         redis.set("session:user:gitlab:#{user.id}:6919a6f1bb119dd7396fadc38fd18d0d", '')
@@ -244,8 +249,9 @@ RSpec.describe ActiveSession, :clean_gitlab_redis_shared_state do
 
     it 'removes the devise session' do
       Gitlab::Redis::SharedState.with do |redis|
-        redis.set("session:user:gitlab:#{user.id}:6919a6f1bb119dd7396fadc38fd18d0d", '')
-        redis.set("session:gitlab:6919a6f1bb119dd7396fadc38fd18d0d", '')
+        redis.set("session:user:gitlab:#{user.id}:#{rack_session.public_id}", '')
+        # Emulate redis-rack: https://github.com/redis-store/redis-rack/blob/c75f7f1a6016ee224e2615017fbfee964f23a837/lib/rack/session/redis.rb#L88
+        redis.set("session:gitlab:#{rack_session.private_id}", '')
       end
 
       ActiveSession.destroy(user, request.session.id)
@@ -322,7 +328,7 @@ RSpec.describe ActiveSession, :clean_gitlab_redis_shared_state do
           (1..max_number_of_sessions_plus_two).each do |number|
             redis.set(
               "session:user:gitlab:#{user.id}:#{number}",
-              Marshal.dump(ActiveSession.new(session_id: "#{number}", updated_at: number.days.ago))
+              Marshal.dump(ActiveSession.new(session_id: number.to_s, updated_at: number.days.ago))
             )
             redis.sadd(
               "session:lookup:user:gitlab:#{user.id}",
diff --git a/spec/services/groups/destroy_service_spec.rb b/spec/services/groups/destroy_service_spec.rb
index a45c7cdffa641be03850332caf962568aef5f124..bf639153b9926a1eaed238c8f20e6ba051ea24de 100644
--- a/spec/services/groups/destroy_service_spec.rb
+++ b/spec/services/groups/destroy_service_spec.rb
@@ -133,4 +133,55 @@ describe Groups::DestroyService do
       end
     end
   end
+
+  describe 'authorization updates', :sidekiq_inline do
+    context 'shared groups' do
+      let!(:shared_group) { create(:group, :private) }
+      let!(:shared_group_child) { create(:group, :private, parent: shared_group) }
+
+      let!(:project) { create(:project, group: shared_group) }
+      let!(:project_child) { create(:project, group: shared_group_child) }
+
+      before do
+        create(:group_group_link, shared_group: shared_group, shared_with_group: group)
+        group.refresh_members_authorized_projects
+      end
+
+      it 'updates project authorization' do
+        expect(user.can?(:read_project, project)).to eq(true)
+        expect(user.can?(:read_project, project_child)).to eq(true)
+
+        destroy_group(group, user, false)
+
+        expect(user.can?(:read_project, project)).to eq(false)
+        expect(user.can?(:read_project, project_child)).to eq(false)
+      end
+    end
+
+    context 'shared groups in the same group hierarchy' do
+      let!(:subgroup) { create(:group, :private, parent: group) }
+      let!(:subgroup_user) { create(:user) }
+
+      before do
+        subgroup.add_user(subgroup_user, Gitlab::Access::MAINTAINER)
+
+        create(:group_group_link, shared_group: group, shared_with_group: subgroup)
+        subgroup.refresh_members_authorized_projects
+      end
+
+      context 'group is deleted' do
+        it 'updates project authorization' do
+          expect { destroy_group(group, user, false) }.to(
+            change { subgroup_user.can?(:read_project, project) }.from(true).to(false))
+        end
+      end
+
+      context 'subgroup is deleted' do
+        it 'updates project authorization' do
+          expect { destroy_group(subgroup, user, false) }.to(
+            change { subgroup_user.can?(:read_project, project) }.from(true).to(false))
+        end
+      end
+    end
+  end
 end
diff --git a/spec/support/rails/test_case_patch.rb b/spec/support/rails/test_case_patch.rb
new file mode 100644
index 0000000000000000000000000000000000000000..161e1ef2a4c980e64ebd77746b0838d8c321b001
--- /dev/null
+++ b/spec/support/rails/test_case_patch.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+#
+# This file pulls in the changes in https://github.com/rails/rails/pull/38063
+# to fix controller specs updated with the latest Rack versions.
+#
+# This file should be removed after that change ships. It is not
+# present in Rails 6.0.2.2.
+module ActionController
+  class TestRequest < ActionDispatch::TestRequest #:nodoc:
+    def self.new_session
+      TestSessionPatched.new
+    end
+  end
+
+  # Methods #destroy and #load! are overridden to avoid calling methods on the
+  # @store object, which does not exist for the TestSession class.
+  class TestSessionPatched < Rack::Session::Abstract::PersistedSecure::SecureSessionHash #:nodoc:
+    DEFAULT_OPTIONS = Rack::Session::Abstract::Persisted::DEFAULT_OPTIONS
+
+    def initialize(session = {})
+      super(nil, nil)
+      @id = Rack::Session::SessionId.new(SecureRandom.hex(16))
+      @data = stringify_keys(session)
+      @loaded = true
+    end
+
+    def exists?
+      true
+    end
+
+    def keys
+      @data.keys
+    end
+
+    def values
+      @data.values
+    end
+
+    def destroy
+      clear
+    end
+
+    def fetch(key, *args, &block)
+      @data.fetch(key.to_s, *args, &block)
+    end
+
+    private
+
+    def load!
+      @id
+    end
+  end
+end