    public function getFilePath($fileName = null)
    {
        if ($fileName === null) {
            $fileName = $this->fileName;
        }

        // Limit paths to those under the assets directory
        $directory = $this->theme->getPath() . '/' . $this->dirName . '/';
        $path = realpath($directory . $fileName);
        if (!starts_with($path, $directory)) {
            return false;
        }

        return $path;
    }
The product uses an externally controlled name or reference that resolves to a resource that is outside of the intended control sphere.