CVE-2025-23889: FooGallery Captions XSS Vulnerability

CVE-2025-23889 Overview

CVE-2025-23889 is a Reflected Cross-Site Scripting (XSS) vulnerability affecting the FooGallery Captions WordPress plugin developed by tormorten. This vulnerability arises from improper neutralization of user input during web page generation, allowing attackers to inject malicious scripts that execute in the context of a victim's browser session.

The vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation) and affects all versions of the FooGallery Captions plugin through version 1.0.2. When exploited, attackers can craft malicious URLs that, when clicked by unsuspecting users, execute arbitrary JavaScript code in the victim's browser.

Critical Impact

Successful exploitation allows attackers to steal session cookies, hijack user accounts, perform actions on behalf of authenticated users, deface website content, or redirect victims to malicious sites.

Affected Products

• FooGallery Captions WordPress Plugin versions up to and including 1.0.2
• WordPress websites utilizing the vulnerable foogallery-captions plugin
• Any web application integrating the affected FooGallery Captions component

Discovery Timeline

• 2025-01-24 - CVE-2025-23889 published to NVD
• 2026-04-23 - Last updated in NVD database

Technical Details for CVE-2025-23889

Vulnerability Analysis

This Reflected XSS vulnerability occurs when the FooGallery Captions plugin fails to properly sanitize user-supplied input before reflecting it back in the HTTP response. The plugin does not adequately escape special HTML characters in certain input parameters, allowing malicious script content to be embedded in dynamically generated pages.

Reflected XSS attacks require user interaction—typically clicking a crafted malicious link. Once the victim navigates to the URL containing the malicious payload, the script executes within the security context of the vulnerable WordPress site, giving the attacker access to sensitive information such as session tokens and the ability to perform authenticated actions.

The attack can be executed remotely over the network with no authentication required, though user interaction (clicking the malicious link) is necessary for successful exploitation. The impact extends beyond the vulnerable application's origin due to the scope change characteristic, potentially affecting other sites or contexts.

Root Cause

The root cause of CVE-2025-23889 is insufficient input validation and output encoding within the FooGallery Captions plugin. The plugin fails to implement proper sanitization mechanisms when processing user-controllable input that is subsequently rendered in HTML output. This oversight allows specially crafted input containing JavaScript code to bypass security filters and execute in the victim's browser.

WordPress plugins that handle user input without leveraging WordPress's built-in escaping functions such as esc_html(), esc_attr(), or wp_kses() are particularly susceptible to XSS vulnerabilities.

Attack Vector

The attack vector for this vulnerability is network-based, requiring an attacker to craft a malicious URL containing the XSS payload and social engineer a victim into clicking the link. The attacker typically embeds the malicious URL in phishing emails, forum posts, social media messages, or compromised websites.

When the victim clicks the link, their browser sends a request to the vulnerable WordPress site with the malicious payload embedded in the URL parameters. The server processes the request and reflects the unsanitized input back in the response, causing the victim's browser to execute the attacker's JavaScript code.

The vulnerability can be exploited to perform session hijacking by stealing authentication cookies, modify displayed content to conduct phishing attacks, redirect users to malicious external sites, or perform unauthorized actions using the victim's authenticated session. For detailed technical information, refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2025-23889

Indicators of Compromise

• Unusual HTTP requests containing script tags or JavaScript event handlers in URL parameters targeting FooGallery Captions endpoints
• Web server logs showing encoded characters (%3C, %3E, %22) in query strings associated with the plugin
• Reports from users about unexpected browser behavior or redirects when visiting gallery pages
• Anomalous outbound connections from user browsers to unknown external domains after visiting the site

Detection Strategies

• Deploy Web Application Firewalls (WAF) with rules to detect and block common XSS payloads in request parameters
• Implement Content Security Policy (CSP) headers to restrict script execution sources and detect policy violations
• Monitor web server access logs for requests containing suspicious patterns like <script>, javascript:, or encoded equivalents
• Use browser-based security tools and extensions to detect reflected content execution anomalies

Monitoring Recommendations

• Enable verbose logging on WordPress installations to capture detailed request information for security analysis
• Configure real-time alerting for WAF rule triggers associated with XSS attack patterns
• Regularly audit installed WordPress plugins for known vulnerabilities using automated scanning tools
• Monitor CSP violation reports to identify potential XSS exploitation attempts

How to Mitigate CVE-2025-23889

Immediate Actions Required

• Deactivate and remove the FooGallery Captions plugin (foogallery-captions) until a patched version is available
• Audit web server logs for evidence of exploitation attempts targeting the vulnerable plugin
• Implement WAF rules to block requests containing XSS payloads targeting the affected plugin endpoints
• Notify site administrators and users about the vulnerability and recommend caution with unsolicited links

Patch Information

As of the last update, versions through 1.0.2 remain vulnerable. Site administrators should check for updates from the plugin developer (tormorten) and apply any security patches as soon as they become available. Monitor the Patchstack vulnerability database for updated information regarding fixes.

Workarounds

• Remove or deactivate the FooGallery Captions plugin entirely if the functionality is not critical
• Deploy a Web Application Firewall with XSS protection rules to filter malicious input
• Implement strict Content Security Policy headers to mitigate the impact of successful XSS attacks
• Consider alternative gallery caption solutions that have undergone recent security audits

# WordPress CLI commands to deactivate the vulnerable plugin
wp plugin deactivate foogallery-captions --path=/var/www/html/wordpress

# Verify plugin is deactivated
wp plugin list --status=inactive --path=/var/www/html/wordpress | grep foogallery-captions

# Add CSP header in Apache configuration (.htaccess)
# Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none';"