XSS Archives - Sucuri Labs

Unauthenticated Stored Cross Site Scripting in WP Product...

Exploitation Level: Very Easy / Remote

DREAD Score: 7.4

Vulnerability: Persistent Cross-site Scripting

Patched Version: 3.7.6

During a routine research audit for our Sucuri Firewall, we discovered an Unauthenticated Persistent Cross-Site Scripting (XSS) affecting 40,000+ users of the WP Product Review plugin.

Current State of the Vulnerability

Though this security bug was fixed in the 3.7.6 release, older versions can be exploited by an attacker without any account in the vulnerable site. We are not aware of any exploit attempts currently using this vulnerability.

Disclosure / Response Timeline:

May 13, 2020: Initial contact.
May 14, 2020: Patch is live.

Technical Details

All user input data is sanitized but the WordPress function used can be bypassed when the parameter is set inside an HTML attribute. A successful attack results in malicious scripts being injected in all the site’s products.

Update as Soon as Possible

Unauthenticated attacks are very serious because they can be automated, making it easy for hackers to mount successful, widespread attacks against vulnerable websites. The number of active installs, the ease of exploitation, and the effects of a successful attack are what makes this vulnerability particularly dangerous.

To protect against this vulnerability, we strongly encourage WP Product Review users to update their plugin to version 3.7.6 as soon as possible. Users that are unable to update immediately can leverage the Sucuri Firewall or equivalent technology to virtually patch the vulnerability.

May 14, 2020 by John Castro

Reflected XSS in Cookiebot Administrative Page

A reflected XSS vulnerability has recently been found in the Cookiebot plugin plugin, impacting a user base of over 40k installs. Versions prior to 3.6.1 are susceptible to this attack, which allows hackers to exploit the vulnerability found on administrative pages.

This vulnerability is caused by the manual tabs mechanism, which tries to add a class to the form with the current tab.

<?php if ( isset( $_GET['tab'] ) ) {
     $active_tab = $_GET['tab'];
} else if ( $active_tab == 'unavailable_addons' ) {
     $active_tab = 'unavailable_addons';
} else {
     $active_tab = 'available_addons';
} ?>

// ...

<form method="post" action="options.php" class="<?php echo $active_tab; ?>">

The issue lies in the fact that only two tab types should be present: available_addons or unavailable_addons. These values are never checked, however, and are directly inserted into the form class attribute.

This improper implementation leads to the potential for a reflected cross-site scripting attack which relies on human behavior - such as an administrator visiting a link.
If the website administrator visits an attacker’s specially crafted URL, the bad actor may be able to compromise and take over the website.

Timeline:

2020-03-11: Initial disclosure
2020-03-12: Version 3.6.1 released

Mitigation Steps:

Websites using Cookiebot versions lower than 3.6.1 should update their plugins to the latest patch immediately to mitigate risk. As always, customers using our WAF are protected from this issue with our virtual patching technology.

Mar 23, 2020 by Antony Garand

Reflected XSS in Advanced Ads Admin Dashboard

A patch for a vulnerability in the Advanced Ads plugin has been released. Prior to version 1.17.4, attackers were able to exploit two reflected XSS attacks via the admin dashboard.

Both vulnerabilities are related to the advads-last-edited-group property, which should normally be a number.

As the argument in this property was not sanitized, a malicious payload can be injected into websites using vulnerable versions of this plugin, causing up to two reflected XSS on the page.

$last_edited_group_id = 0;
if ( isset( $_REQUEST['advads-last-edited-group'] ) ) {
        $last_edited_group_id = $_REQUEST['advads-last-edited-group'];
        ?>
        <script>
                var body = document.getElementsByTagName("body")[0];
                body.addEventListener("load", function(){
                        jQuery('#advads-ad-group-<?php echo $last_edited_group_id; ?>').get(0).scrollIntoView(false);
                }, true);
        </script>
        <?php
}// ...
<div id="advads-ad-group-list">
        <form action="" method="post" id="advads-form-groups">
                <?php wp_nonce_field( 'update-advads-groups', 'advads-group-update-nonce' ); ?>
                <table class="wp-list-table widefat fixed adgroups">
                        <?php $ad_groups_list->render_header(); ?>
                        <?php $ad_groups_list->render_rows(); ?>
                </table>
<input type="hidden" name="advads-last-edited-group" id="advads-last-edited-group" value="<?php echo $last_edited_group_id; ?>"/>
                <div class="tablenav bottom">
                        <?php submit_button( __( 'Update Groups', 'advanced-ads' ) ); ?>
                </div>
        </form>
</div>

If a website administrator visits an attacker’s specially crafted link, the bad actor may be able to gain access to the compromised environment and obtain access to the account.

Timeline:

2020-03-08: Initial disclosure
2020-03-09: Update provided by the developer
2020-03-09: Version 1.17.4 released

Mitigation Steps:

Websites with Ads Admin versions lower than 1.17.4 should update their plugins to the latest patch immediately to mitigate risk. As always, customers using our WAF are protected from this issue with our virtual patching technology.

Mar 17, 2020 by Antony Garand

Stored XSS in Elementor

Exploitation Level: Easy/Requires Authentication
DREAD Score: 8.0
Vulnerability: Stored XSS
Patched Version: 2.7.6

During a routine audit of WordPress plugins last december, we discovered a Stored XSS vulnerability in the very popular Elementor Page Builder plugin, which powers no less than 3 million+ websites according to the official active installs count.

Are You Affected?

This vulnerability is exploitable on sites which allow users to have accounts and are using Elementor versions lower than 2.7.6, released last December.

A successful attack results in malicious scripts being injected on the plugin’s System Info page. If an administrator visits that page, the malicious Javascript code can execute privileged actions on the victim’s behalf, like creating new administrative accounts or storing backdoors on the site to maintain access.

Indicators of Compromise

This vulnerability can be exploited via the WordPress AJAX endpoint /wp-admin/admin-ajax.php.

Depending on the exploit, website owners may be able to flag attacks in access logs by looking for requests from unknown IPs containing action=elementor_js_log in the request.

Conclusion & Mitigation Steps

To protect against this vulnerability, we strongly encourage users of the Elementor Page Builder to update their site to the latest version available as soon as possible — 2.8.5 at the time of writing.

Users who are unable to update immediately can leverage the Sucuri Firewall or equivalent technology to virtually patch the vulnerability.

Jan 29, 2020 by MarcAlexandre Montpas

Wrong content-type to XSS

WordPress Social Sharing Plugin – Sassy Social Share, which currently has over 100000 installations just fixed a Cross Site Scripting Vulnerability. This bug allows attackers to send custom links that direct unsuspecting users toward a vulnerable page. From this page, they often employ a variety of methods to trigger their proof of concept.

Let’s take a look to the patch:

+++ b/sassy-social-share.new/public/class-sassy-social-share-public.php
@@ -1511,6 +1511,7 @@ class Sassy_Social_Share_Public {
        private function ajax_response( $response ) {
                $response = apply_filters( 'heateor_sss_ajax_response_filter', $response );
+               header( 'Content-Type: application/json' );
                die( json_encode( $response ) );

        }
@@ -1540,7 +1541,7 @@ class Sassy_Social_Share_Public {
                if ( isset( $_GET['urls'] ) && count( $_GET['urls'] ) > 0 ) {
                        $target_urls = array_unique( $_GET['urls'] );
                        foreach ( $target_urls as $k => $v ) {
-                               $target_urls[$k] = esc_attr( $v );
+                               $target_urls[esc_attr( $k )] = esc_attr( $v );
                        }
                }

JSON data returned to the user didn’t have a content type defined in the function _ajaxresponse() and the default is html. This together with the following snipped allowing any authenticated user consume that endpoint makes this bug really easy for attackers to exploit:

includes/class-sassy-social-share.php
205:        add_action( 'wp_ajax_heateor_sss_sharing_count', array( $plugin_public, 'fetch_share_counts' ) );
206:        add_action( 'wp_ajax_nopriv_heateor_sss_sharing_count', array( $plugin_public, 'fetch_share_counts' ) );

Because of the nature of the bug, and due this issue was already fixed, we can share a simple PoC that shows how a malicious link abusing this vulnerability might be presented:

http://vulnerablesite.com/wp-admin/admin-ajax.php?action=heateor_sss_sharing_count&urls[<h onmouseover%3Dalert(1)>]=hola.com&urls[1]=hola2.com

If you have an old version of this plugin installed please update to the latest version (3.3.4) asap. You can add a WAF as a second layer of protection and virtually patch the vulnerability.

Nov 22, 2019 by John Castro