diff --git a/app/controllers/invitations_controller.rb b/app/controllers/invitations_controller.rb
index 5dbca1e43..88bd6043a 100644
--- a/app/controllers/invitations_controller.rb
+++ b/app/controllers/invitations_controller.rb
@@ -1,4 +1,10 @@
 class InvitationsController < ApplicationController
+  # The invitation token in the URL is the authenticator for these actions;
+  # CSRF is redundant and fails when browsers withhold the session cookie
+  # (e.g. Safari/WebKit ITP on cross-site navigation). Same rationale as
+  # FeedbackController#submit (PR #2641, Rollbar #535).
+  skip_forgery_protection only: %i[attend reject]
+
   before_action :require_login, only: [:index]
   before_action :set_invitation, only: %i[show attend reject]
 
diff --git a/app/controllers/waiting_lists_controller.rb b/app/controllers/waiting_lists_controller.rb
index b922e3bde..37df15a16 100644
--- a/app/controllers/waiting_lists_controller.rb
+++ b/app/controllers/waiting_lists_controller.rb
@@ -1,6 +1,12 @@
 class WaitingListsController < ApplicationController
   include WorkshopInvitationConcerns
 
+  # The invitation token in the URL is the authenticator for these actions;
+  # CSRF is redundant and fails when browsers withhold the session cookie
+  # (e.g. Safari/WebKit ITP on cross-site navigation). Same rationale as
+  # FeedbackController#submit (PR #2641, Rollbar #535).
+  skip_forgery_protection only: %i[create destroy]
+
   def create
     @invitation.assign_attributes(invitation_params)
 
diff --git a/app/controllers/workshop_invitation_controller.rb b/app/controllers/workshop_invitation_controller.rb
index 91a3fba8c..e9166437c 100644
--- a/app/controllers/workshop_invitation_controller.rb
+++ b/app/controllers/workshop_invitation_controller.rb
@@ -5,6 +5,12 @@ class WorkshopInvitationController < ApplicationController
   # It provides accept/reject RSVP actions for workshop attendees via token-based links.
   # Routes: /invitation/:token (legacy) and /workshop_invitation/:token
 
+  # The invitation token in the URL is the authenticator for these actions;
+  # CSRF is redundant and fails when browsers withhold the session cookie
+  # (e.g. Safari/WebKit ITP on cross-site navigation). Same rationale as
+  # FeedbackController#submit (PR #2641, Rollbar #535).
+  skip_forgery_protection only: %i[update accept]
+
   def show
     @announcements = @invitation.member.announcements.active
     @tutorial_titles = Tutorial.all_titles
diff --git a/spec/controllers/feedback_controller_spec.rb b/spec/controllers/feedback_controller_spec.rb
index cdac0bfd2..046c32098 100644
--- a/spec/controllers/feedback_controller_spec.rb
+++ b/spec/controllers/feedback_controller_spec.rb
@@ -63,13 +63,13 @@
     end
 
     context 'without a CSRF token (browser did not send session cookie)' do
-      it 'still accepts the feedback submission' do
-        # Simulate the real-world scenario where the browser withholds the
-        # session cookie (e.g. Safari ITP, cross-site navigation, or cookie
-        # blocking). With protect_from_forgery enabled, this would normally
-        # raise ActionController::InvalidAuthenticityToken.
-        ActionController::Base.allow_forgery_protection = true
+      # Simulate the real-world scenario where the browser withholds the
+      # session cookie (e.g. Safari/WebKit ITP, cross-site navigation, or cookie
+      # blocking). With protect_from_forgery enabled, this would normally
+      # raise ActionController::InvalidAuthenticityToken.
+      include_context 'with forgery protection enforced'
 
+      it 'still accepts the feedback submission' do
         patch :submit, params: {
           id: feedback_request.token,
           feedback: {
@@ -84,8 +84,6 @@
         expect(response).to redirect_to(root_path)
         expect(flash[:notice]).to eq(I18n.t('messages.feedback_saved'))
         expect(feedback_request.reload.submited).to be true
-      ensure
-        ActionController::Base.allow_forgery_protection = false
       end
     end
   end
diff --git a/spec/controllers/invitations_controller_spec.rb b/spec/controllers/invitations_controller_spec.rb
index 830cce365..ef90d4d1e 100644
--- a/spec/controllers/invitations_controller_spec.rb
+++ b/spec/controllers/invitations_controller_spec.rb
@@ -17,6 +17,20 @@
         expect(response).to have_http_status(:not_found)
       end
     end
+
+    context 'without a CSRF token (browser did not send session cookie)' do
+      # Simulate the real-world scenario where the browser withholds the
+      # session cookie (e.g. Safari/WebKit ITP on cross-site navigation).
+      # The invitation token in the URL is the authenticator.
+      include_context 'with forgery protection enforced'
+      let(:invitation) { Fabricate(:coach_invitation, event:) }
+
+      it 'still accepts the RSVP' do
+        post :attend, params: { event_id: event.id, token: invitation.token }
+
+        expect(invitation.reload.attending).to be true
+      end
+    end
   end
 
   describe 'POST #reject' do
@@ -26,5 +40,16 @@
         expect(response).to have_http_status(:not_found)
       end
     end
+
+    context 'without a CSRF token (browser did not send session cookie)' do
+      include_context 'with forgery protection enforced'
+      let(:invitation) { Fabricate(:attending_event_invitation, event:) }
+
+      it 'still cancels the RSVP' do
+        post :reject, params: { event_id: event.id, token: invitation.token }
+
+        expect(invitation.reload.attending).to be false
+      end
+    end
   end
 end
diff --git a/spec/controllers/waiting_lists_controller_spec.rb b/spec/controllers/waiting_lists_controller_spec.rb
index 6df4c2bc5..47ca54650 100644
--- a/spec/controllers/waiting_lists_controller_spec.rb
+++ b/spec/controllers/waiting_lists_controller_spec.rb
@@ -30,5 +30,33 @@
 
       expect(WaitingList.where(invitation:).count).to eq(1)
     end
+
+    context 'without a CSRF token (browser did not send session cookie)' do
+      # Simulate the real-world scenario where the browser withholds the
+      # session cookie (e.g. Safari/WebKit ITP on cross-site navigation).
+      # The invitation token in the URL is the authenticator.
+      include_context 'with forgery protection enforced'
+
+      it 'still adds the member to the waiting list' do
+        expect do
+          post :create, params: { invitation_id: invitation.token }
+        end.to change(WaitingList, :count).by(1)
+      end
+    end
+  end
+
+  describe 'DELETE #destroy' do
+    context 'without a CSRF token (browser did not send session cookie)' do
+      include_context 'with forgery protection enforced'
+
+      it 'still removes the member from the waiting list' do
+        waiting_list = Fabricate(:waiting_list)
+        invitation = waiting_list.invitation
+
+        expect do
+          delete :destroy, params: { invitation_id: invitation.token }
+        end.to change(WaitingList, :count).by(-1)
+      end
+    end
   end
 end
diff --git a/spec/controllers/workshop_invitation_controller_spec.rb b/spec/controllers/workshop_invitation_controller_spec.rb
index a7b38f929..d8f5665ed 100644
--- a/spec/controllers/workshop_invitation_controller_spec.rb
+++ b/spec/controllers/workshop_invitation_controller_spec.rb
@@ -93,6 +93,19 @@
         expect(flash[:notice].join).to include('Tutorial')
       end
     end
+
+    context 'without a CSRF token (browser did not send session cookie)' do
+      # Simulate the real-world scenario where the browser withholds the
+      # session cookie (e.g. Safari/WebKit ITP on cross-site navigation).
+      # The invitation token in the URL is the authenticator.
+      include_context 'with forgery protection enforced'
+
+      it 'still accepts the RSVP' do
+        post :accept, params: { id: invitation.token }
+
+        expect(invitation.reload.attending).to be true
+      end
+    end
   end
 
   describe 'POST #reject' do
@@ -184,5 +197,17 @@
         expect(flash[:notice].join).to include('Tutorial')
       end
     end
+
+    context 'without a CSRF token (browser did not send session cookie)' do
+      include_context 'with forgery protection enforced'
+
+      it 'still updates the invitation details' do
+        new_tutorial = Fabricate(:tutorial)
+
+        patch :update, params: { id: invitation.token, workshop_invitation: { tutorial: new_tutorial.title } }
+
+        expect(invitation.reload.tutorial).to eq(new_tutorial.title)
+      end
+    end
   end
 end
diff --git a/spec/support/shared_contexts/forgery_protection.rb b/spec/support/shared_contexts/forgery_protection.rb
new file mode 100644
index 000000000..9e4dd6b22
--- /dev/null
+++ b/spec/support/shared_contexts/forgery_protection.rb
@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+RSpec.shared_context 'with forgery protection enforced' do
+  before { ActionController::Base.allow_forgery_protection = true }
+  after  { ActionController::Base.allow_forgery_protection = false }
+end