From 76572581aa359b0529a5572d69b7e8f764e3bc71 Mon Sep 17 00:00:00 2001
From: "Alexander M. Turek" <me@derrabus.de>
Date: Sun, 23 May 2021 20:50:38 +0200
Subject: [PATCH] Add an upgrade note about the removal of Serializable

---
 UPGRADE-6.0.md | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/UPGRADE-6.0.md b/UPGRADE-6.0.md
index 87fe763d6e..82c722ef9e 100644
--- a/UPGRADE-6.0.md
+++ b/UPGRADE-6.0.md
@@ -158,6 +158,11 @@ Security
    in `PreAuthenticatedToken`, `RememberMeToken`, `SwitchUserToken`, `UsernamePasswordToken`,
    `DefaultAuthenticationSuccessHandler`.
  * Removed the `AbstractRememberMeServices::$providerKey` property in favor of `AbstractRememberMeServices::$firewallName`
+ * Authentication tokens do not implement the deprecated `Serializable`
+   interface anymore. The consequence is that tokens that were serialized (e.g.
+   into the session) with PHP 7.3 or below cannot be unserialized anymore. It is
+   recommended to roll out a Symfony 5 application with PHP 7.4 or later first
+   before upgrading it to Symfony 6.
 
 TwigBundle
 ----------