Deserialization of Untrusted Data in Codeigniter4

CodeIgniter is an open source PHP full-stack web framework. Deserialization of Untrusted Data was found in the `old()` function in CodeIgniter4. Remote attackers may inject auto-loadable arbitrary objects with this vulnerability, and possibly execute existing PHP code on the server. We are aware of a working exploit, which can lead to SQL injection. Users are advised to upgrade to v4.1.6 or later. Users unable to upgrade as advised to not use the `old()` function and form_helper nor `RedirectResponse::withInput()` and `redirect()->withInput()`.