CVE-2025-23836: Custom Coming Soon Plugin XSS Vulnerability

CVE-2025-23836 Overview

CVE-2025-23836 is a Reflected Cross-Site Scripting (XSS) vulnerability affecting the Custom Coming Soon plugin for WordPress, developed by SuryaBhan. This security flaw arises from improper neutralization of 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 occur when user-supplied input is immediately returned by a web application in an error message, search result, or any other response that includes some or all of the input without proper sanitization. In the case of this WordPress plugin, attackers can craft malicious URLs that, when clicked by authenticated users, execute arbitrary JavaScript code within their browser context.

Critical Impact

Attackers can steal session cookies, hijack user sessions, deface websites, or redirect users to malicious sites by exploiting this reflected XSS vulnerability in the Custom Coming Soon plugin.

Affected Products

• Custom Coming Soon WordPress Plugin version 2.2 and earlier
• WordPress installations running affected versions of custom-coming-soon
• All websites utilizing the vulnerable plugin without proper input validation patches

Discovery Timeline

• 2025-01-23 - CVE-2025-23836 published to NVD
• 2026-04-23 - Last updated in NVD database

Technical Details for CVE-2025-23836

Vulnerability Analysis

This vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation), which encompasses Cross-Site Scripting flaws. The Custom Coming Soon plugin fails to properly sanitize user-controlled input before reflecting it back in the HTML response, creating an opportunity for script injection attacks.

The attack requires user interaction, as victims must click on a crafted malicious link or visit a compromised page containing the exploit payload. Once executed, the injected script runs with the same privileges as the victim user, potentially allowing attackers to perform actions on their behalf, access sensitive data, or compromise the WordPress administration panel if an administrator is targeted.

The vulnerability has a changed scope impact, meaning successful exploitation can affect resources beyond the vulnerable component's security scope. This is particularly concerning in WordPress environments where compromising an administrator session could lead to full site takeover.

Root Cause

The root cause of CVE-2025-23836 lies in insufficient input validation and output encoding within the Custom Coming Soon plugin. When user input is passed through URL parameters or form fields, the plugin fails to apply proper sanitization functions such as esc_html(), esc_attr(), or wp_kses() before rendering the content in the browser.

WordPress provides numerous built-in escaping functions specifically designed to prevent XSS attacks. The absence of these security controls in the plugin's code path allows raw user input containing HTML and JavaScript to be interpreted by the browser as executable code rather than inert text.

Attack Vector

The attack vector for this reflected XSS vulnerability is network-based, requiring an attacker to craft a malicious URL containing the XSS payload and convince a victim to click on it. Common delivery mechanisms include:

The attacker constructs a URL targeting a vulnerable endpoint in the Custom Coming Soon plugin, embedding JavaScript code within URL parameters. When the victim clicks the link, their browser requests the page from the vulnerable WordPress site. The server processes the request and reflects the malicious input back in the response without proper encoding. The victim's browser interprets the reflected content as legitimate script code and executes it within the security context of the WordPress site.

This vulnerability is documented in the Patchstack Vulnerability Report which provides additional technical context for security researchers.

Detection Methods for CVE-2025-23836

Indicators of Compromise

• Unusual URL parameters containing encoded JavaScript or HTML tags in web server access logs
• Referrer headers showing suspicious external domains linking to your WordPress site with complex query strings
• User reports of unexpected redirects or pop-ups when accessing the website
• Browser console errors indicating blocked cross-origin requests from unfamiliar domains

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block common XSS payloads in URL parameters
• Monitor access logs for URL patterns containing typical XSS indicators such as <script>, javascript:, onerror=, and encoded variants
• Deploy browser-based XSS auditors and Content Security Policy headers to detect and report injection attempts
• Conduct regular security scans of your WordPress installation using tools that identify vulnerable plugin versions

Monitoring Recommendations

• Enable detailed logging for the Custom Coming Soon plugin and associated WordPress endpoints
• Configure real-time alerting for patterns matching XSS attack signatures in your log management platform
• Review HTTP request logs for suspicious URL encoding patterns such as %3Cscript%3E or double-encoded payloads
• Implement Content Security Policy (CSP) reporting to capture attempted violations from injected scripts

How to Mitigate CVE-2025-23836

Immediate Actions Required

• Update the Custom Coming Soon plugin to a patched version as soon as one becomes available from the developer
• Temporarily deactivate the Custom Coming Soon plugin if immediate patching is not possible to eliminate the attack surface
• Implement Content Security Policy headers to restrict script execution sources and mitigate XSS impact
• Review web server logs for evidence of exploitation attempts targeting this vulnerability

Patch Information

Organizations should check the Patchstack Vulnerability Report for the latest remediation guidance and patch availability. As this vulnerability affects Custom Coming Soon version 2.2 and earlier, ensure your plugin is updated to a version that addresses this XSS flaw once released by SuryaBhan.

Until a patch is available, implementing defense-in-depth measures such as WAF rules and CSP headers can significantly reduce the risk of successful exploitation.

Workarounds

• Implement strict Content Security Policy headers to prevent execution of inline scripts and restrict script sources to trusted domains only
• Deploy a Web Application Firewall with XSS-specific rulesets to filter malicious payloads before they reach the WordPress application
• Consider using alternative coming soon or maintenance mode plugins that have undergone security audits
• Apply virtual patching through your WAF or security plugin to block known attack patterns for this vulnerability

# Add Content Security Policy headers to Apache configuration
# Add to .htaccess or Apache vhost configuration
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; frame-ancestors 'self';"
Header set X-Content-Type-Options "nosniff"
Header set X-XSS-Protection "1; mode=block"