CVE-2026-63223: CodeIgniter: Uploaded file extension validation bypass in `is_image` and `mime_in` rules

This is an unsafe file upload validation vulnerability that can lead to remote code execution in vulnerable application configurations.

Applications are impacted when they:

• validate uploads using is_image or mime_in without an independent safe extension check, such as ext_in on patched versions
• save uploaded files using the client-supplied filename
• place uploads in a web-accessible directory where PHP files can execute