diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index d803602c063d08c47be702450c98f24a22891c0b..2e9de6b8d57817decbb88d59119cc67db407d9ff 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -1400,14 +1400,6 @@ Rails/HasManyOrHasOneDependent:
     - 'app/models/user.rb'
     - 'app/models/web/push_subscription.rb'
 
-# Configuration parameters: Include.
-# Include: app/helpers/**/*.rb
-Rails/HelperInstanceVariable:
-  Exclude:
-    - 'app/helpers/application_helper.rb'
-    - 'app/helpers/instance_helper.rb'
-    - 'app/helpers/jsonld_helper.rb'
-
 # This cop supports safe autocorrection (--autocorrect).
 # Configuration parameters: Include.
 # Include: spec/**/*, test/**/*
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index c06aae10b0e195333b039ac1277002e978fd3fcc..d59fe88105cc73058be8f919c32593a939844684 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -19,6 +19,7 @@ class ApplicationController < ActionController::Base
   helper_method :omniauth_only?
   helper_method :sso_account_settings
   helper_method :whitelist_mode?
+  helper_method :body_class_string
 
   rescue_from ActionController::ParameterMissing, Paperclip::AdapterRegistry::NoHandlerError, with: :bad_request
   rescue_from Mastodon::NotPermittedError, with: :forbidden
@@ -148,6 +149,10 @@ class ApplicationController < ActionController::Base
     current_user.setting_theme
   end
 
+  def body_class_string
+    @body_classes || ''
+  end
+
   def respond_with_error(code)
     respond_to do |format|
       format.any  { render "errors/#{code}", layout: 'error', status: code, formats: [:html] }
diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 828688b04d5efd786bb0282a2653f7b9186a9c33..9a30cfbc6b0f809186e93044fa9c1926badd5f00 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -168,7 +168,7 @@ module ApplicationHelper
   end
 
   def body_classes
-    output = (@body_classes || '').split
+    output = body_class_string.split
     output << "theme-#{current_theme.parameterize}"
     output << 'system-font' if current_account&.user&.setting_system_font_ui
     output << (current_account&.user&.setting_reduce_motion ? 'reduce-motion' : 'no-reduce-motion')
diff --git a/app/helpers/instance_helper.rb b/app/helpers/instance_helper.rb
index bedfe6f3048b0ae29a6525356180f57767a7e052..893afdd51ff10075e82c19c0f63adae09ac7b320 100644
--- a/app/helpers/instance_helper.rb
+++ b/app/helpers/instance_helper.rb
@@ -9,13 +9,17 @@ module InstanceHelper
     @site_hostname ||= Addressable::URI.parse("//#{Rails.configuration.x.local_domain}").display_uri.host
   end
 
-  def description_for_sign_up
-    prefix = if @invite.present?
-               I18n.t('auth.description.prefix_invited_by_user', name: @invite.user.account.username)
-             else
-               I18n.t('auth.description.prefix_sign_up')
-             end
+  def description_for_sign_up(invite = nil)
+    safe_join([description_prefix(invite), I18n.t('auth.description.suffix')], ' ')
+  end
+
+  private
 
-    safe_join([prefix, I18n.t('auth.description.suffix')], ' ')
+  def description_prefix(invite)
+    if invite.present?
+      I18n.t('auth.description.prefix_invited_by_user', name: invite.user.account.username)
+    else
+      I18n.t('auth.description.prefix_sign_up')
+    end
   end
 end
diff --git a/app/helpers/jsonld_helper.rb b/app/helpers/jsonld_helper.rb
index 24362b61e79544bdf0f99c56a6b00f3ae45b11ad..ce3ff094f6bdd422847bffb47d3f8463a673dff6 100644
--- a/app/helpers/jsonld_helper.rb
+++ b/app/helpers/jsonld_helper.rb
@@ -63,11 +63,11 @@ module JsonLdHelper
     uri.nil? || !uri.start_with?('http://', 'https://')
   end
 
-  def invalid_origin?(url)
-    return true if unsupported_uri_scheme?(url)
+  def non_matching_uri_hosts?(base_url, comparison_url)
+    return true if unsupported_uri_scheme?(comparison_url)
 
-    needle   = Addressable::URI.parse(url).host
-    haystack = Addressable::URI.parse(@account.uri).host
+    needle = Addressable::URI.parse(comparison_url).host
+    haystack = Addressable::URI.parse(base_url).host
 
     !haystack.casecmp(needle).zero?
   end
diff --git a/app/lib/activitypub/activity/create.rb b/app/lib/activitypub/activity/create.rb
index e2355bfbcc557c1097ecb210c072fb3a9ed39956..23fbabf4cc1d13bc1e1fbf048090b7e7f25a582c 100644
--- a/app/lib/activitypub/activity/create.rb
+++ b/app/lib/activitypub/activity/create.rb
@@ -17,7 +17,7 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
   private
 
   def create_encrypted_message
-    return reject_payload! if invalid_origin?(object_uri) || @options[:delivered_to_account_id].blank?
+    return reject_payload! if non_matching_uri_hosts?(@account.uri, object_uri) || @options[:delivered_to_account_id].blank?
 
     target_account = Account.find(@options[:delivered_to_account_id])
     target_device  = target_account.devices.find_by(device_id: @object.dig('to', 'deviceId'))
@@ -45,7 +45,7 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
   end
 
   def create_status
-    return reject_payload! if unsupported_object_type? || invalid_origin?(object_uri) || tombstone_exists? || !related_to_local_activity?
+    return reject_payload! if unsupported_object_type? || non_matching_uri_hosts?(@account.uri, object_uri) || tombstone_exists? || !related_to_local_activity?
 
     with_lock("create:#{object_uri}") do
       return if delete_arrived_first?(object_uri) || poll_vote?
diff --git a/app/lib/activitypub/activity/delete.rb b/app/lib/activitypub/activity/delete.rb
index 871eb39667af6473feff89b588fae3da2deb4799..3af500f2b195088199ed5562cdccde373109f927 100644
--- a/app/lib/activitypub/activity/delete.rb
+++ b/app/lib/activitypub/activity/delete.rb
@@ -21,7 +21,7 @@ class ActivityPub::Activity::Delete < ActivityPub::Activity
     return if object_uri.nil?
 
     with_lock("delete_status_in_progress:#{object_uri}", raise_on_failure: false) do
-      unless invalid_origin?(object_uri)
+      unless non_matching_uri_hosts?(@account.uri, object_uri)
         # This lock ensures a concurrent `ActivityPub::Activity::Create` either
         # does not create a status at all, or has finished saving it to the
         # database before we try to load it.
diff --git a/app/lib/activitypub/activity/flag.rb b/app/lib/activitypub/activity/flag.rb
index b0443849a6b8b5de0b142759525070adc9e59153..dc808ad364199dab0348b012830701ffdff30a1a 100644
--- a/app/lib/activitypub/activity/flag.rb
+++ b/app/lib/activitypub/activity/flag.rb
@@ -33,6 +33,6 @@ class ActivityPub::Activity::Flag < ActivityPub::Activity
   end
 
   def report_uri
-    @json['id'] unless @json['id'].nil? || invalid_origin?(@json['id'])
+    @json['id'] unless @json['id'].nil? || non_matching_uri_hosts?(@account.uri, @json['id'])
   end
 end
diff --git a/app/lib/activitypub/activity/update.rb b/app/lib/activitypub/activity/update.rb
index e7c3bc9bf83dec02fcb9ce76855e923691686815..8e72e082378bef685b404cc2a9321d1857565b9a 100644
--- a/app/lib/activitypub/activity/update.rb
+++ b/app/lib/activitypub/activity/update.rb
@@ -22,7 +22,7 @@ class ActivityPub::Activity::Update < ActivityPub::Activity
   end
 
   def update_status
-    return reject_payload! if invalid_origin?(object_uri)
+    return reject_payload! if non_matching_uri_hosts?(@account.uri, object_uri)
 
     @status = Status.find_by(uri: object_uri, account_id: @account.id)
 
diff --git a/app/lib/activitypub/dereferencer.rb b/app/lib/activitypub/dereferencer.rb
index 4d7756d71d880b24dc55d5e006e6730ab17722ee..eb99842828c42dd752857bf4df742ad3d864beef 100644
--- a/app/lib/activitypub/dereferencer.rb
+++ b/app/lib/activitypub/dereferencer.rb
@@ -40,7 +40,7 @@ class ActivityPub::Dereferencer
   end
 
   def perform_request(uri, headers: nil)
-    return if invalid_origin?(uri)
+    return if non_matching_uri_hosts?(@permitted_origin, uri)
 
     req = Request.new(:get, uri)
 
@@ -57,13 +57,4 @@ class ActivityPub::Dereferencer
       end
     end
   end
-
-  def invalid_origin?(uri)
-    return true if unsupported_uri_scheme?(uri)
-
-    needle   = Addressable::URI.parse(uri).host
-    haystack = Addressable::URI.parse(@permitted_origin).host
-
-    !haystack.casecmp(needle).zero?
-  end
 end
diff --git a/app/services/activitypub/fetch_featured_collection_service.rb b/app/services/activitypub/fetch_featured_collection_service.rb
index 1208820df224d63073f8d3eb7df57ba69f88609d..e8a31dade9b07b4788dc8043af336afcd1983024 100644
--- a/app/services/activitypub/fetch_featured_collection_service.rb
+++ b/app/services/activitypub/fetch_featured_collection_service.rb
@@ -31,7 +31,7 @@ class ActivityPub::FetchFeaturedCollectionService < BaseService
 
   def fetch_collection(collection_or_uri)
     return collection_or_uri if collection_or_uri.is_a?(Hash)
-    return if invalid_origin?(collection_or_uri)
+    return if non_matching_uri_hosts?(@account.uri, collection_or_uri)
 
     fetch_resource_without_id_validation(collection_or_uri, local_follower, true)
   end
@@ -46,7 +46,7 @@ class ActivityPub::FetchFeaturedCollectionService < BaseService
       next unless item.is_a?(String) || item['type'] == 'Note'
 
       uri = value_or_id(item)
-      next if ActivityPub::TagManager.instance.local_uri?(uri) || invalid_origin?(uri)
+      next if ActivityPub::TagManager.instance.local_uri?(uri) || non_matching_uri_hosts?(@account.uri, uri)
 
       status = ActivityPub::FetchRemoteStatusService.new.call(uri, on_behalf_of: local_follower, expected_actor_uri: @account.uri, request_id: @options[:request_id])
       next unless status&.account_id == @account.id
diff --git a/app/services/activitypub/fetch_featured_tags_collection_service.rb b/app/services/activitypub/fetch_featured_tags_collection_service.rb
index ff1a88aa1eb35aa5676f2e247dc8961fcbb1e2e8..cb71b37e75e386b39d431b337c37b0b67b13de06 100644
--- a/app/services/activitypub/fetch_featured_tags_collection_service.rb
+++ b/app/services/activitypub/fetch_featured_tags_collection_service.rb
@@ -43,7 +43,7 @@ class ActivityPub::FetchFeaturedTagsCollectionService < BaseService
 
   def fetch_collection(collection_or_uri)
     return collection_or_uri if collection_or_uri.is_a?(Hash)
-    return if invalid_origin?(collection_or_uri)
+    return if non_matching_uri_hosts?(@account.uri, collection_or_uri)
 
     fetch_resource_without_id_validation(collection_or_uri, local_follower, true)
   end
diff --git a/app/services/activitypub/fetch_replies_service.rb b/app/services/activitypub/fetch_replies_service.rb
index 3fe150ba2152ffd2d0946960931e23b75a42da2a..b5c7759ec5ed1b42edefcc5fd895824291825246 100644
--- a/app/services/activitypub/fetch_replies_service.rb
+++ b/app/services/activitypub/fetch_replies_service.rb
@@ -35,7 +35,7 @@ class ActivityPub::FetchRepliesService < BaseService
   def fetch_collection(collection_or_uri)
     return collection_or_uri if collection_or_uri.is_a?(Hash)
     return unless @allow_synchronous_requests
-    return if invalid_origin?(collection_or_uri)
+    return if non_matching_uri_hosts?(@account.uri, collection_or_uri)
 
     fetch_resource_without_id_validation(collection_or_uri, nil, true)
   end
@@ -45,6 +45,6 @@ class ActivityPub::FetchRepliesService < BaseService
     # amplification attacks.
 
     # Also limit to 5 fetched replies to limit potential for DoS.
-    @items.map { |item| value_or_id(item) }.reject { |uri| invalid_origin?(uri) }.take(5)
+    @items.map { |item| value_or_id(item) }.reject { |uri| non_matching_uri_hosts?(@account.uri, uri) }.take(5)
   end
 end
diff --git a/app/services/activitypub/prepare_followers_synchronization_service.rb b/app/services/activitypub/prepare_followers_synchronization_service.rb
index 2d22ed701e8722f8beef2f407d8e8d9b6661d517..56ec0e44bfd0435a807ebc9f0e3c6f237972905a 100644
--- a/app/services/activitypub/prepare_followers_synchronization_service.rb
+++ b/app/services/activitypub/prepare_followers_synchronization_service.rb
@@ -6,7 +6,7 @@ class ActivityPub::PrepareFollowersSynchronizationService < BaseService
   def call(account, params)
     @account = account
 
-    return if params['collectionId'] != @account.followers_url || invalid_origin?(params['url']) || @account.local_followers_hash == params['digest']
+    return if params['collectionId'] != @account.followers_url || non_matching_uri_hosts?(@account.uri, params['url']) || @account.local_followers_hash == params['digest']
 
     ActivityPub::FollowersSynchronizationWorker.perform_async(@account.id, params['url'])
   end
diff --git a/app/services/activitypub/synchronize_followers_service.rb b/app/services/activitypub/synchronize_followers_service.rb
index 93cd60253353cccab9457b753cdc197bede1a383..9bd6034a57235d1a33eee37d579ea96d196e9322 100644
--- a/app/services/activitypub/synchronize_followers_service.rb
+++ b/app/services/activitypub/synchronize_followers_service.rb
@@ -67,7 +67,7 @@ class ActivityPub::SynchronizeFollowersService < BaseService
 
   def fetch_collection(collection_or_uri)
     return collection_or_uri if collection_or_uri.is_a?(Hash)
-    return if invalid_origin?(collection_or_uri)
+    return if non_matching_uri_hosts?(@account.uri, collection_or_uri)
 
     fetch_resource_without_id_validation(collection_or_uri, nil, true)
   end
diff --git a/app/views/auth/registrations/new.html.haml b/app/views/auth/registrations/new.html.haml
index 4df0f95d51977e4c66471ebb4bbe28280b9d4e4e..18511a59644b754485c2254a065a7d9c77ad9159 100644
--- a/app/views/auth/registrations/new.html.haml
+++ b/app/views/auth/registrations/new.html.haml
@@ -2,7 +2,7 @@
   = t('auth.register')
 
 - content_for :header_tags do
-  = render partial: 'shared/og', locals: { description: description_for_sign_up }
+  = render partial: 'shared/og', locals: { description: description_for_sign_up(@invite) }
 
 = simple_form_for(resource, as: resource_name, url: registration_path(resource_name), html: { novalidate: false }) do |f|
   = render 'auth/shared/progress', stage: 'details'
diff --git a/app/views/auth/registrations/rules.html.haml b/app/views/auth/registrations/rules.html.haml
index aa16ab957360e533d267b9379e6fabe7347bab55..ab3fa864abdb4159e78780909ca5c31b465c53a9 100644
--- a/app/views/auth/registrations/rules.html.haml
+++ b/app/views/auth/registrations/rules.html.haml
@@ -2,7 +2,7 @@
   = t('auth.register')
 
 - content_for :header_tags do
-  = render partial: 'shared/og', locals: { description: description_for_sign_up }
+  = render partial: 'shared/og', locals: { description: description_for_sign_up(@invite) }
 
 .simple_form
   = render 'auth/shared/progress', stage: 'rules'
diff --git a/spec/controllers/shares_controller_spec.rb b/spec/controllers/shares_controller_spec.rb
index 6d5bb4f8d8d985d1cdfdc70fa5507dede86f8220..5dcc46e47acf35ee7f32825ddc917e4abb26058e 100644
--- a/spec/controllers/shares_controller_spec.rb
+++ b/spec/controllers/shares_controller_spec.rb
@@ -9,7 +9,7 @@ describe SharesController do
 
   before { sign_in user }
 
-  describe 'GTE #show' do
+  describe 'GET #show' do
     subject(:body_classes) { assigns(:body_classes) }
 
     before { get :show, params: { title: 'test title', text: 'test text', url: 'url1 url2' } }
diff --git a/spec/helpers/application_helper_spec.rb b/spec/helpers/application_helper_spec.rb
index 2db2ee288efd8477b7899ee8f9312eaa778195bc..88751548fc2c470a04482c5ada50aa0a7a1218f0 100644
--- a/spec/helpers/application_helper_spec.rb
+++ b/spec/helpers/application_helper_spec.rb
@@ -27,6 +27,22 @@ describe ApplicationHelper do
     end
   end
 
+  describe 'body_classes' do
+    context 'with a body class string from a controller' do
+      before do
+        without_partial_double_verification do
+          allow(helper).to receive(:body_class_string).and_return('modal-layout compose-standalone')
+          allow(helper).to receive(:current_theme).and_return('default')
+          allow(helper).to receive(:current_account).and_return(Fabricate(:account))
+        end
+      end
+
+      it 'uses the controller body classes in the result' do
+        expect(helper.body_classes).to match(/modal-layout compose-standalone/)
+      end
+    end
+  end
+
   describe 'locale_direction' do
     around do |example|
       current_locale = I18n.locale