    public function addDirective($directive) {
        if (isset($this->directives[$i = $directive->id->toString()])) {
            throw new HTMLPurifier_ConfigSchema_Exception("Cannot redefine directive '$i'");
        }
        $this->directives[$i] = $directive;
    }
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.