A Session Fixation issue exists in CodeIgniter before 3.1.9 because session.use_strict_mode in the Session Library was mishandled.
https://github.com/advisories/GHSA-g434-3q2j-hj4r
https://www.codeigniter.com/user_guide/changelog.html
https://github.com/bcit-ci/CodeIgniter/commit/800a20d6c4662d99ae0988b2f8f2238bb8bb29db