As reported at:

http://www.securityfocus.com/bid/39858

There was a vulnerability issue in our new dj-classifieds extension.

This was already fixed.

New version is available to download here: dj-classifieds-0.9.2.

If you're already using dj-classifieds extension you can fix the issue manually:

In file components/com_djclassifieds/controller.php
near line 428 replace:

for ($i = 0; $i < count($pliki['name']); $i++)
    {
        if (substr($pliki['type'][$i], 0, 5) == "image")
        {
                $nazwa = md5(microtime()).$pliki['name'][$i];;
                $images .= $nazwa;
                $images .= ";";
                $sciezka = JPATH_BASE."/components/com_djclassifieds/images/".$nazwa;
                move_uploaded_file($pliki['tmp_name'][$i], $sciezka);
                $this->makeimg($sciezka);
                if ($i == 0)
                {
                    $this->makeimg_s($sciezka);
                } //tylko dla pierwszego obrazka miniaturka
        }
    }

to:

for ($i = 0; $i < count($pliki['name']); $i++)
    {
        if (substr($pliki['type'][$i], 0, 5) == "image")
        {
            $s_f = getimagesize($pliki['tmp_name'][$i]);
            if(is_array($s_f) && $s_f[0] > 2){
                $nazwa = md5(microtime()).$pliki['name'][$i];;
                $images .= $nazwa;
                $images .= ";";
                $sciezka = JPATH_BASE."/components/com_djclassifieds/images/".$nazwa;
                move_uploaded_file($pliki['tmp_name'][$i], $sciezka);
                $this->makeimg($sciezka);
                if ($i == 0)
                {
                    $this->makeimg_s($sciezka);
                } //tylko dla pierwszego obrazka miniaturka
            }
        }
    }