--- a/components/content_settings/core/browser/cookie_settings.cc	2017-10-04 18:07:38.000000000 -0400
+++ b/components/content_settings/core/browser/cookie_settings.cc	2017-10-08 18:59:16.257098393 -0400
@@ -80,7 +80,7 @@
 void CookieSettings::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterBooleanPref(
-      prefs::kBlockThirdPartyCookies, false,
+      prefs::kBlockThirdPartyCookies, true,
       user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
 }