    function visitTextNode(\JBBCode\TextNode $textNode)
    {
        /* Convert :) into an image tag. */
        $textNode->setValue(str_replace(':)', 
                                        '<img src="/smiley.png" alt=":)" />', 
                                        $textNode->getValue()));
    }
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.