diff --git a/app/controllers/api/v1/instances/extended_descriptions_controller.rb b/app/controllers/api/v1/instances/extended_descriptions_controller.rb
index 17cf0d790da..a0665725bd3 100644
--- a/app/controllers/api/v1/instances/extended_descriptions_controller.rb
+++ b/app/controllers/api/v1/instances/extended_descriptions_controller.rb
@@ -2,11 +2,17 @@
 
 class Api::V1::Instances::ExtendedDescriptionsController < Api::BaseController
   skip_before_action :require_authenticated_user!, unless: :whitelist_mode?
+  skip_around_action :set_locale
 
   before_action :set_extended_description
 
   vary_by ''
 
+  # Override `current_user` to avoid reading session cookies unless in whitelist mode
+  def current_user
+    super if whitelist_mode?
+  end
+
   def show
     cache_even_if_authenticated!
     render json: @extended_description, serializer: REST::ExtendedDescriptionSerializer
diff --git a/app/controllers/api/v1/instances/peers_controller.rb b/app/controllers/api/v1/instances/peers_controller.rb
index 20809d75533..70281362a8c 100644
--- a/app/controllers/api/v1/instances/peers_controller.rb
+++ b/app/controllers/api/v1/instances/peers_controller.rb
@@ -4,9 +4,15 @@ class Api::V1::Instances::PeersController < Api::BaseController
   before_action :require_enabled_api!
 
   skip_before_action :require_authenticated_user!, unless: :whitelist_mode?
+  skip_around_action :set_locale
 
   vary_by ''
 
+  # Override `current_user` to avoid reading session cookies unless in whitelist mode
+  def current_user
+    super if whitelist_mode?
+  end
+
   def index
     cache_even_if_authenticated!
     render_with_cache(expires_in: 1.day) { Instance.where.not(domain: DomainBlock.select(:domain)).pluck(:domain) }
diff --git a/app/controllers/api/v1/instances/rules_controller.rb b/app/controllers/api/v1/instances/rules_controller.rb
index cd5cc7b0867..d3eeca32624 100644
--- a/app/controllers/api/v1/instances/rules_controller.rb
+++ b/app/controllers/api/v1/instances/rules_controller.rb
@@ -2,11 +2,17 @@
 
 class Api::V1::Instances::RulesController < Api::BaseController
   skip_before_action :require_authenticated_user!, unless: :whitelist_mode?
+  skip_around_action :set_locale
 
   before_action :set_rules
 
   vary_by ''
 
+  # Override `current_user` to avoid reading session cookies unless in whitelist mode
+  def current_user
+    super if whitelist_mode?
+  end
+
   def index
     cache_even_if_authenticated!
     render json: @rules, each_serializer: REST::RuleSerializer
diff --git a/app/controllers/api/v1/instances_controller.rb b/app/controllers/api/v1/instances_controller.rb
index d4c822e64ae..5a6701ff96b 100644
--- a/app/controllers/api/v1/instances_controller.rb
+++ b/app/controllers/api/v1/instances_controller.rb
@@ -2,9 +2,15 @@
 
 class Api::V1::InstancesController < Api::BaseController
   skip_before_action :require_authenticated_user!, unless: :whitelist_mode?
+  skip_around_action :set_locale
 
   vary_by ''
 
+  # Override `current_user` to avoid reading session cookies unless in whitelist mode
+  def current_user
+    super if whitelist_mode?
+  end
+
   def show
     cache_even_if_authenticated!
     render_with_cache json: InstancePresenter.new, serializer: REST::V1::InstanceSerializer, root: 'instance'
diff --git a/app/controllers/manifests_controller.rb b/app/controllers/manifests_controller.rb
index 593b76c5368..4fba9198f3b 100644
--- a/app/controllers/manifests_controller.rb
+++ b/app/controllers/manifests_controller.rb
@@ -1,6 +1,10 @@
 # frozen_string_literal: true
 
 class ManifestsController < ActionController::Base # rubocop:disable Rails/ApplicationController
+  # Prevent `active_model_serializer`'s `ActionController::Serialization` from calling `current_user`
+  # and thus re-issuing session cookies
+  serialization_scope nil
+
   def show
     expires_in 3.minutes, public: true
     render json: InstancePresenter.new, serializer: ManifestSerializer, root: 'instance'
diff --git a/app/controllers/well_known/nodeinfo_controller.rb b/app/controllers/well_known/nodeinfo_controller.rb
index ab6b8f5a405..e20e8c62a0c 100644
--- a/app/controllers/well_known/nodeinfo_controller.rb
+++ b/app/controllers/well_known/nodeinfo_controller.rb
@@ -4,6 +4,10 @@ module WellKnown
   class NodeInfoController < ActionController::Base # rubocop:disable Rails/ApplicationController
     include CacheConcern
 
+    # Prevent `active_model_serializer`'s `ActionController::Serialization` from calling `current_user`
+    # and thus re-issuing session cookies
+    serialization_scope nil
+
     def index
       expires_in 3.days, public: true
       render_with_cache json: {}, serializer: NodeInfo::DiscoverySerializer, adapter: NodeInfo::Adapter, expires_in: 3.days, root: 'nodeinfo'