CVE-2025-28958: Bg Orthodox Calendar CSRF Vulnerability

CVE-2025-28958 Overview

CVE-2025-28958 is a Cross-Site Request Forgery (CSRF) vulnerability in the WordPress Bg Orthodox Calendar plugin developed by Vadim Bogaiskov. This vulnerability allows attackers to exploit the lack of proper CSRF token validation to inject malicious scripts that persist in the application, resulting in Stored Cross-Site Scripting (XSS). The chained CSRF to Stored XSS attack vector significantly increases the potential impact, as attackers can trick authenticated administrators into unknowingly executing malicious requests that permanently store harmful scripts within the plugin's settings or content areas.

Critical Impact

Attackers can leverage CSRF to inject persistent malicious scripts that execute in the browsers of any user viewing affected pages, potentially leading to session hijacking, credential theft, or administrative account compromise.

Affected Products

• WordPress Bg Orthodox Calendar plugin version 0.13.10 and earlier
• All WordPress installations using affected versions of bg-orthodox-calendar

Discovery Timeline

• 2025-06-06 - CVE-2025-28958 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2025-28958

Vulnerability Analysis

This vulnerability combines two distinct attack vectors into a potent exploit chain. The CSRF vulnerability (CWE-352) exists due to missing or improper validation of anti-CSRF tokens in the plugin's administrative functions. When an authenticated administrator is tricked into clicking a malicious link or visiting a compromised page, the attacker can force the victim's browser to submit unauthorized requests to the plugin's backend.

The second component of the attack chain is the Stored XSS vulnerability. Once the CSRF protection is bypassed, attackers can inject malicious JavaScript code that gets permanently stored in the WordPress database. This stored payload then executes whenever users or administrators view pages where the injected content is rendered.

The combination of these vulnerabilities is particularly dangerous because it transforms a client-side attack requiring user interaction (CSRF) into a persistent threat that can affect all users of the WordPress site.

Root Cause

The root cause of this vulnerability stems from two security oversights in the plugin's implementation:

1. Missing CSRF Token Validation: The plugin fails to implement or properly verify WordPress nonces (security tokens) in forms and AJAX handlers that modify plugin settings or content. Without these tokens, the server cannot distinguish between legitimate user-initiated requests and forged requests from malicious third-party sites.

2. Insufficient Output Sanitization: User-supplied input is stored in the database without proper sanitization and subsequently rendered on pages without adequate output encoding, allowing malicious script content to execute in users' browsers.

Attack Vector

The attack follows a multi-stage exploitation process:

1. Reconnaissance: The attacker identifies a WordPress site running a vulnerable version of the Bg Orthodox Calendar plugin.

2. Payload Crafting: The attacker creates a malicious HTML page containing a hidden form that targets the plugin's vulnerable endpoint. This form includes JavaScript payload designed to be stored persistently.

3. Social Engineering: The attacker tricks an authenticated WordPress administrator into visiting the malicious page, often through phishing emails, compromised websites, or malicious advertisements.

4. CSRF Exploitation: When the administrator's browser loads the malicious page, JavaScript automatically submits the hidden form to the WordPress site, carrying the administrator's authenticated session cookies.

5. Persistent XSS Storage: The malicious script payload is stored in the WordPress database through the plugin's vulnerable functionality.

6. Payload Execution: Subsequently, when any user or administrator views pages containing the injected content, the malicious JavaScript executes in their browser context.

The exploitation mechanism leverages the implicit trust between a user's browser and the WordPress site, bypassing same-origin policy protections through the forged cross-site request. For detailed technical analysis, refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2025-28958

Indicators of Compromise

• Unexpected or unauthorized modifications to Bg Orthodox Calendar plugin settings
• Suspicious JavaScript code in plugin database entries or WordPress options table
• Unusual outbound network connections from client browsers when viewing calendar pages
• Administrator accounts reporting unexpected session behavior or credential theft
• Web server logs showing POST requests to plugin endpoints from external referrers

Detection Strategies

• Monitor WordPress audit logs for changes to the Bg Orthodox Calendar plugin settings by unknown or suspicious sources
• Implement Content Security Policy (CSP) headers to detect and block unauthorized script execution
• Deploy Web Application Firewall (WAF) rules to detect and block CSRF attack patterns targeting WordPress plugins
• Regularly scan WordPress database tables for embedded script tags or suspicious JavaScript patterns
• Review browser console logs for unexpected script execution when visiting pages with calendar functionality

Monitoring Recommendations

• Enable WordPress debug logging to capture plugin-related errors and suspicious activity
• Configure real-time alerting for changes to plugin configuration options in the wp_options table
• Implement file integrity monitoring on WordPress core files and plugin directories
• Monitor for unusual patterns in HTTP Referer headers on administrative POST requests
• Deploy endpoint detection solutions to identify potential credential harvesting attempts following XSS exploitation

How to Mitigate CVE-2025-28958

Immediate Actions Required

• Update the Bg Orthodox Calendar plugin to a patched version when available from the vendor
• If no patch is available, consider temporarily deactivating the bg-orthodox-calendar plugin until a fix is released
• Review and audit all plugin settings for unauthorized modifications or suspicious content
• Implement additional CSRF protection at the server level using WordPress security plugins
• Educate administrators about phishing risks and the importance of verifying links before clicking

Patch Information

At the time of this analysis, administrators should check the official WordPress plugin repository and the Patchstack vulnerability database for updates regarding a security patch. Users running version 0.13.10 or earlier are affected and should prioritize updating once a fix becomes available.

Workarounds

• Implement server-level CSRF protection using security plugins such as Wordfence or Sucuri that add additional token validation
• Restrict administrative access to trusted IP addresses using .htaccess or firewall rules
• Add Content Security Policy headers to limit script execution sources and mitigate XSS impact
• Use browser extensions or security configurations that block cross-origin form submissions
• Consider replacing the vulnerable plugin with an alternative calendar solution until the vulnerability is patched

# WordPress .htaccess configuration to restrict admin access by IP
# Add to wp-admin/.htaccess file
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{REMOTE_ADDR} !^192\.168\.1\.100$
RewriteCond %{REMOTE_ADDR} !^10\.0\.0\.50$
RewriteRule ^(.*)$ - [F,L]
</IfModule>