Fix CSP headers being unintendedly wide (#26105)

config/initializers/content_security_policy.rb

@@ -3,7 +3,7 @@
 # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
 
 def host_to_url(str)
-  "http#{Rails.configuration.x.use_https ? 's' : ''}://#{str}".split('/').first if str.present?
+  "http#{Rails.configuration.x.use_https ? 's' : ''}://#{str.split('/').first}" if str.present?
 end
 
 base_host = Rails.configuration.x.web_domain

spec/requests/content_security_policy_spec.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe 'Content-Security-Policy' do
+  it 'sets the expected CSP headers' do
+    allow(SecureRandom).to receive(:base64).with(16).and_return('ZbA+JmE7+bK8F5qvADZHuQ==')
+
+    get '/'
+    expect(response.headers['Content-Security-Policy'].split(';').map(&:strip)).to contain_exactly(
+      "base-uri 'none'",
+      "default-src 'none'",
+      "frame-ancestors 'none'",
+      "font-src 'self' https://cb6e6126.ngrok.io",
+      "img-src 'self' https: data: blob: https://cb6e6126.ngrok.io",
+      "style-src 'self' https://cb6e6126.ngrok.io 'nonce-ZbA+JmE7+bK8F5qvADZHuQ=='",
+      "media-src 'self' https: data: https://cb6e6126.ngrok.io",
+      "frame-src 'self' https:",
+      "manifest-src 'self' https://cb6e6126.ngrok.io",
+      "form-action 'self'",
+      "child-src 'self' blob: https://cb6e6126.ngrok.io",
+      "worker-src 'self' blob: https://cb6e6126.ngrok.io",
+      "connect-src 'self' data: blob: https://cb6e6126.ngrok.io https://cb6e6126.ngrok.io ws://localhost:4000",
+      "script-src 'self' https://cb6e6126.ngrok.io"
+    )
+  end
+end