usd-2024-0009 | Reflected XSS in Oveleon Cookiebar

Details

Advisory ID: usd-2024-0009
Product: Cookiebar
Affected Version: 2.X
Vulnerability Type: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Security Risk: HIGH, CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N
Vendor URL: https://www.usd.de/
Vendor acknowledged vulnerability: Yes
Vendor Status: Fixed
CVE Number: Not requested yet
CVE Link: Not requested yet
First Published: Published
Last Update: 2024-07-29

Affected Component

The block function in CookiebarController.php.

Desciption

Oveleon's Cookiebar is an extension for the popular Contao CMS.
The block/locale endpoint does not properly sanitize the user-controlled locale input before including it in the backend's HTTP response, thereby causing reflected XSS.

Proof of Concept

The vulnerability could be triggered by entering the following Link:

https://[redacted].de/cookiebar/block/dens82w%22%3E%3Cimg%20src%3da%20onerror%3dalert(1)%3Ew9qt
n/[id]?redirect=https%3A%2F%2Fwww.youtube.com%2Fembed%2FqNNfPzs4YAA%3Fautoplay%3D1%26amp%3Biv_load_policy%3D3%26amp%3Bmo
destbranding%3D1%26amp%3Brel%3D0

It is likely related to the following function in the Oveleon Cookiebar source code:

    /**
     * Block content
     *
     * @Route("/cookiebar/block/{locale}/{id}", name="cookiebar_block")
     */
    public function block(Request $request, string $locale, int $id): Response
    {
        System::loadLanguageFile('tl_cookiebar', $locale);

        $this->framework->initialize();

        $objCookie = CookieModel::findById($id);

        if (null === $objCookie || null === $request->headers->get('referer'))
        {
            throw new PageNotFoundException();
        }

        $strUrl = $request->get('redirect');

        // Protect against XSS attacks
        if(!Validator::isUrl($strUrl))
        {
            return new Response('The redirect destination must be a valid URL.', Response::HTTP_BAD_REQUEST);
        }

        $objTemplate = new FrontendTemplate($objCookie->blockTemplate ?: 'ccb_element_blocker');

        $objTemplate->language = $locale;
        $objTemplate->id = $objCookie->id;
        $objTemplate->title = $objCookie->title;
        $objTemplate->type = $objCookie->type;
        $objTemplate->iframeType = $objCookie->iframeType;
        $objTemplate->description = $objCookie->blockDescription;
        $objTemplate->redirect = $request->get('redirect');
        $objTemplate->acceptAndDisplayLabel = $this->translator->trans('tl_cookiebar.acceptAndDisplayLabel', [], 'contao_default', $locale);

        return $objTemplate->getResponse();
    }

Fix

Sanitize the locale input to prevent XSS payloads from being executed in a user's browser.

References

• https://github.com/oveleon/contao-cookiebar/blob/2.x/src/Controller/CookiebarController.php
• https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html

Timeline

• 2024-04-24: Vulnerability discovered by DR of usd AG.
• 2024-07-25: Probable cause of the vulnerability has been identified as Oveleon's Cookiebar Extension for Contao CMS.
• 2024-07-25: Vulnerability disclosed via GitHub Vulnerability Report.

Credits

This security vulnerability was identified by DR of usd AG.

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Disclaimer

The information provided in this security advisory is provided "as is" and without warranty of any kind. Details of this security advisory may be updated in order to provide as accurate information as possible.