CVE-2026-25465: CP Multi View Event Calendar XSS Flaw

CVE-2026-25465 Overview

CVE-2026-25465 is a Stored Cross-Site Scripting (XSS) vulnerability affecting the CP Multi View Event Calendar WordPress plugin (cp-multi-view-calendar). This vulnerability arises from improper neutralization of input during web page generation, allowing attackers with low privileges to inject malicious scripts that persist in the application and execute when other users view affected pages.

Critical Impact

Authenticated attackers can inject persistent malicious scripts that execute in the browsers of other users, potentially leading to session hijacking, credential theft, or unauthorized actions within the WordPress admin context.

Affected Products

• CP Multi View Event Calendar plugin versions through 1.4.35
• WordPress installations running vulnerable versions of cp-multi-view-calendar
• Websites with user-generated calendar event content

Discovery Timeline

• 2026-03-25 - CVE-2026-25465 published to NVD
• 2026-03-25 - Last updated in NVD database

Technical Details for CVE-2026-25465

Vulnerability Analysis

This Stored XSS vulnerability (CWE-79) exists due to insufficient input sanitization and output encoding within the CP Multi View Event Calendar plugin. When users with authenticated access create or modify calendar events, the application fails to properly neutralize potentially malicious input before storing it in the database and rendering it back to other users.

The vulnerability requires network access with low attack complexity. An attacker needs low-level privileges (such as a contributor or subscriber role depending on plugin configuration) and must lure a victim into viewing the malicious content. The changed scope indicates that the vulnerability can impact resources beyond the vulnerable component, affecting other users' browser sessions.

The impact includes low-level compromise of confidentiality, integrity, and availability. Attackers can steal session cookies, modify displayed content, redirect users to malicious sites, or perform actions on behalf of authenticated administrators.

Root Cause

The root cause stems from inadequate input validation and output encoding in the event calendar management functionality. User-supplied data within event fields is stored directly in the database without proper sanitization and rendered in web pages without appropriate encoding, allowing HTML and JavaScript code to execute in victims' browsers.

Attack Vector

The attack requires an authenticated user with permissions to create or edit calendar events. The attacker crafts malicious JavaScript payloads within event fields (such as event titles, descriptions, or custom fields). When administrators or other users view these calendar entries through the WordPress frontend or admin panel, the malicious script executes within their browser context.

This stored nature of the XSS makes it particularly dangerous as the payload persists and can affect multiple victims over time without requiring continuous attacker interaction.

Detection Methods for CVE-2026-25465

Indicators of Compromise

• Unusual JavaScript code or HTML tags within calendar event database entries
• Event fields containing encoded script tags (<script>, <img onerror=, <svg onload=)
• Unexpected outbound network requests from user browsers when viewing calendar pages
• Reports of unusual browser behavior or redirects when accessing calendar functionality

Detection Strategies

• Implement web application firewall (WAF) rules to detect XSS payloads in form submissions
• Monitor WordPress database tables associated with the calendar plugin for suspicious HTML/JavaScript content
• Enable Content Security Policy (CSP) headers to detect and block inline script execution
• Review plugin logs for unusual event creation or modification patterns

Monitoring Recommendations

• Enable browser developer tools network monitoring when investigating suspected compromise
• Monitor server access logs for patterns indicating automated exploitation attempts
• Set up alerts for failed CSP violations that may indicate blocked XSS attempts
• Regularly audit user-generated calendar content for malicious payloads

How to Mitigate CVE-2026-25465

Immediate Actions Required

• Update CP Multi View Event Calendar plugin to a patched version when available
• Audit existing calendar events for any suspicious JavaScript or HTML content
• Restrict user permissions to limit who can create or modify calendar events
• Implement Content Security Policy headers to mitigate impact of successful exploitation

Patch Information

A security patch addressing this vulnerability should be obtained from the plugin developer. Monitor the Patchstack XSS Vulnerability Report for updated remediation guidance. Until a patch is available, consider disabling the plugin or implementing compensating controls.

Workarounds

• Disable the plugin temporarily if it is not critical to operations
• Restrict event creation and editing to trusted administrator accounts only
• Implement a Web Application Firewall with XSS filtering capabilities
• Add strict Content Security Policy headers to prevent inline script execution

# Add CSP headers to Apache configuration
# Add to .htaccess or Apache config file
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline';"