CVE-2025-49866: Cookie Consent Banner XSS Vulnerability

CVE-2025-49866 Overview

CVE-2025-49866 is a Reflected Cross-Site Scripting (XSS) vulnerability affecting the Beautiful Cookie Consent Banner WordPress plugin developed by Nikel. This vulnerability arises from improper neutralization of user-supplied input during web page generation, allowing attackers to inject malicious scripts that execute in the context of a victim's browser session.

Reflected XSS vulnerabilities in WordPress plugins pose a significant risk to website administrators and visitors, as they can be leveraged for session hijacking, credential theft, defacement, or as a vector for delivering more sophisticated attacks.

Critical Impact

Attackers can craft malicious URLs that, when clicked by authenticated administrators or users, execute arbitrary JavaScript in their browser context, potentially leading to session hijacking, privilege escalation, or further compromise of the WordPress installation.

Affected Products

• Beautiful Cookie Consent Banner (beautiful-and-responsive-cookie-consent) versions up to and including 4.6.1
• WordPress installations running the vulnerable plugin versions

Discovery Timeline

• 2025-07-04 - CVE-2025-49866 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-49866

Vulnerability Analysis

This vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The Beautiful Cookie Consent Banner plugin fails to properly sanitize user-controlled input before reflecting it back in the HTTP response, enabling attackers to inject malicious client-side scripts.

In Reflected XSS attacks, the malicious payload is embedded within a URL or form submission. When a victim clicks a crafted link or submits a manipulated form, the server processes the request and reflects the unsanitized input back to the user's browser, where the injected script executes with the same privileges as the legitimate website content.

Root Cause

The vulnerability stems from insufficient input validation and output encoding within the plugin's request handling logic. When processing user input, the plugin fails to:

1. Validate input against expected patterns and character sets
2. Sanitize special characters that have meaning in HTML/JavaScript contexts
3. Apply proper output encoding (such as HTML entity encoding) before rendering user-supplied data

This allows attackers to break out of the intended data context and inject executable script tags or event handlers.

Attack Vector

An attacker exploiting this vulnerability would craft a malicious URL containing JavaScript payload embedded in a vulnerable parameter. The attack requires user interaction—specifically, the victim must click the malicious link while authenticated to the WordPress site.

The attack flow typically proceeds as follows:

1. Attacker identifies the vulnerable parameter in the Beautiful Cookie Consent Banner plugin
2. Attacker crafts a malicious URL containing the XSS payload
3. Attacker distributes the URL via phishing emails, social media, or compromised websites
4. Victim clicks the link while logged into their WordPress site
5. The malicious script executes in the victim's browser, potentially stealing session cookies or performing actions on behalf of the user

The vulnerability requires no authentication to exploit but does require social engineering to deliver the malicious URL to the victim. For detailed technical analysis, refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2025-49866

Indicators of Compromise

• Unusual URL patterns in web server access logs containing encoded JavaScript payloads or suspicious parameter values targeting the Beautiful Cookie Consent Banner plugin
• User reports of unexpected browser behavior, pop-ups, or redirects when visiting the WordPress site
• Evidence of session hijacking or unauthorized administrative actions that correlate with users clicking external links
• Presence of encoded script tags (%3Cscript%3E) or event handlers in HTTP request parameters

Detection Strategies

• Deploy Web Application Firewall (WAF) rules to detect and block common XSS patterns in request parameters targeting WordPress plugins
• Implement Content Security Policy (CSP) headers to mitigate the impact of successful XSS exploitation by restricting script execution sources
• Monitor web server logs for requests containing suspicious payloads such as <script>, javascript:, onerror=, or similar XSS vectors
• Utilize WordPress security plugins that scan for known vulnerable plugin versions

Monitoring Recommendations

• Enable verbose logging for the WordPress installation and monitor for anomalous plugin-related requests
• Set up real-time alerting for HTTP requests containing common XSS payload signatures
• Periodically review installed plugin versions against known vulnerability databases
• Monitor for unauthorized changes to WordPress user accounts or site configurations that could indicate post-exploitation activity

How to Mitigate CVE-2025-49866

Immediate Actions Required

• Update the Beautiful Cookie Consent Banner plugin to a version newer than 4.6.1 when a patched version becomes available
• If no patch is available, consider temporarily deactivating the plugin until a fix is released
• Implement a Web Application Firewall with XSS protection rules as an additional defense layer
• Educate site administrators about the risks of clicking untrusted links while logged into WordPress

Patch Information

Monitor the plugin's official WordPress repository and the vendor's communications for security updates. The vulnerability was reported through Patchstack, and additional details are available in their vulnerability database entry. Site administrators should subscribe to security advisories for timely notification when patches are released.

Workarounds

• Implement Content Security Policy headers to restrict inline script execution and limit the impact of XSS attacks
• Deploy a WAF rule to filter requests containing potential XSS payloads targeting the affected plugin endpoints
• Temporarily disable or remove the Beautiful Cookie Consent Banner plugin if it is not critical to site functionality
• Restrict administrative access to trusted IP addresses to reduce the attack surface for session hijacking attempts

# Add Content Security Policy header in .htaccess (Apache)
<IfModule mod_headers.c>
    Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none';"
</IfModule>

# Or in nginx configuration
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none';" always;