CI4MS is a CodeIgniter 4-based CMS skeleton that delivers a production-ready, modular architecture with RBAC authorization and theme support. Prior to version 0.31.5.0, ci4ms Theme::upload extracts user uploaded ZIP archives without validating entry names, allowing an authenticated backend user with the theme create permission to write files to arbitrary filesystem locations (Zip Slip) and achieve remote code execution by dropping a PHP file under the public web root. This issue has been patched in version 0.31.5.0.

Affected: Packagist: ci4-cms-erp/ci4ms

### Summary ci4ms Theme::upload extracts user uploaded ZIP archives without validating entry names, allowing an authenticated backend user with the theme create permission to write files to arbitrary filesystem locations (Zip Slip) and achieve remote code execution by dropping a PHP file under the public web root.

### Details modules/Theme/Controllers/Theme.php:13-56 implements the theme upload action. ZipArchive::extractTo() is called directly with no iteration over entry names to verify they resolve inside the destination:

```php public function upload() { $valData = ([ 'theme' => ['label' => lang('Theme.backendTheme'), 'rules' => 'uploaded[theme]|ext_in[theme,zip]|mime_in[theme,...]'], ]); if ($this->validate($valData) == false) return redirect()->route('backendThemes')->withInput()->with('errors', $this->validator->getErrors()); $file = $this->request->getFile('theme'); $tempPath = WRITEPATH . 'tmp/' . str_replace('_theme.zip', '', $file->getName()) . '/'; $zip = new \ZipArchive(); if ($zip->open($file->getTempName()) === true) { $zip->extractTo($tempPath); // no entry-name validation $zip->close(); } ... $log = install_theme_from_tmp($themeName); ... } ```

A ZIP containing entries like `../../public/shell.php` is extracted outside `writable/tmp/` into directories served by PHP. The author validates entries correctly in modules/Methods/Controllers/Methods.php:165-175 with a realpath + regex loop; the…