CI4MS is a CodeIgniter 4-based content management system skeleton. Prior to version 0.31.9.0, the custom "html_purify" validation rule used to sanitize blog post bodies relies on by-reference mutation ("?string &$str"), but CodeIgniter 4's validator passes a local copy of the value, so the sanitized text is silently discarded. The Blog controller writes "$lanData['content']" directly into "blog_langs.content", and the public template echoes it without escaping — yielding stored XSS executable in any visitor's browser, including the superadmin when previewing or editing posts. Version 0.31.9.0 patches the issue.