Plugin Name	WP-CalDav2ICS
Type of Vulnerability	CSRF (Cross-Site Request Forgery)
CVE Number	CVE-2025-59131
Urgency	High
CVE Publish Date	2025-12-30
Source URL	CVE-2025-59131

WP-CalDav2ICS (≤ 1.3.4) CSRF Vulnerability — Critical Security Advisory for WordPress Administrators by Managed-WP

Author: Managed-WP Security Team
Date: 2025-12-30
Tags: WordPress, vulnerability, CSRF, WAF, plugin-security, incident-response

TL;DR

A critical Cross-Site Request Forgery (CSRF) vulnerability (CVE-2025-59131) has been disclosed impacting WP-CalDav2ICS versions ≤ 1.3.4. The root cause is insufficient request validation on plugin actions, which allows attackers to trick privileged WordPress users into unknowingly executing unauthorized operations by visiting malicious content.

This vulnerability poses a significant risk to any site using the affected plugin with privileged admin or editor accounts. No official patch was available at disclosure. Managed-WP customers benefit from immediate protection through custom rule sets and virtual patching that block identified attack patterns. This article provides a thorough risk overview, exploitation scenarios, detection strategies, and practical guidance on long-term defenses.

---

Contents

• Executive summary
• Understanding CSRF and its impact on WordPress
• Overview of the disclosed WP-CalDav2ICS vulnerability
• Potential exploitation scenarios in the wild
• Technical root causes at a high level
• Why public exploit code is not shared
• Risk evaluation and CVSS considerations
• Immediate protective actions for site owners
• Managed-WP mitigation services and recommendations
• Detection and investigation best practices
• Recommended long-term fixes for developers and site managers
• Operational security best practices to reduce exposure
• Free protection plan introduction
• Appendix: commands and inspection tips for admins

---

Executive summary

Cross-Site Request Forgery (CSRF) vulnerabilities remain a prevalent threat in web environments like WordPress where plugins expose sensitive actions without proper verification. The WP-CalDav2ICS plugin’s flaw lets attackers exploit absent or weak validation to coerce authenticated privileged users into executing unintended state-changing requests.

If your site uses WP-CalDav2ICS (version 1.3.4 or below), treat this as a high-priority risk. Disable or restrict the plugin until mitigations are applied, as attackers may silently manipulate settings, exfiltrate data, or escalate privileges leveraging this weakness.

---

Understanding CSRF and its impact on WordPress

CSRF is an attack where a malicious site tricks an authenticated user’s browser into sending unwanted requests to a trusted site. Because the browser automatically attaches valid authentication tokens (cookies, nonces, etc.), the site processes these requests with the user’s permissions.

WordPress is vulnerable to CSRF primarily because:

• Many plugins expose admin-facing endpoints via forms, REST APIs, or AJAX that modify the site state.
• Security relies on nonces (number used once tokens) and capability checks (e.g., current_user_can()) to confirm legitimacy of requests.
• If these validations are missing or insufficient, CSRF attacks can bypass user intentions and modify plugin or site data.

Successful CSRF exploitation can change configurations, create or delete resources, or alter critical settings depending on the plugin’s exposed capabilities.

---

Overview of the disclosed WP-CalDav2ICS vulnerability

• A CSRF vulnerability affects WP-CalDav2ICS versions 1.3.4 and earlier.
• CVE ID: CVE-2025-59131.
• The flaw allows an attacker to send crafted cross-site requests that execute privileged plugin actions when an authenticated admin user visits a malicious page.
• At disclosure, the plugin vendor had not released a patch to address this issue.

Note: This advisory refrains from providing explicit exploit code to prevent misuse. Our focus is on practical risk management and mitigation.

---

Potential exploitation scenarios in the wild

Examples of realistic attack vectors include:

1. Unauthorized modification of calendar sync settings: An attacker forces an admin to unknowingly submit requests that disable or alter synchronization tokens, redirecting or preventing sync.
2. Creation of malicious API credentials: Attackers may create authentication tokens or credentials tied to the plugin, granting them persistent access to calendar or site data.
3. Triggering of unwanted posts or scheduled events: Exploiting vulnerable endpoints to spawn posts, events, or background tasks that could destabilize or misuse resources.
4. Privilege escalation: Using the CSRF attack as a foothold to inject content, create accounts, or establish backdoors for further exploitation.

These exploits require an authenticated privileged user to visit attacker-controlled content while logged into WordPress.

---

Technical root causes at a high level

• Missing or inadequate nonce validation on form submissions and action handlers (absence of check_admin_referer(), wp_verify_nonce()).
• Insufficient capability checks (current_user_can()) in endpoint processing, leading to trust solely on session credentials.
• Use of HTTP GET for state-altering requests, making them vulnerable to simple CSRF.
• REST or AJAX endpoints lacking secure permission_callback implementations or referrer validation.

Plugin developers must rigorously validate both the authenticity and authorization of any request that modifies state.

---

Why public exploit code is not shared

Releasing working exploits for known plugin vulnerabilities dramatically increases risk to users. Managed-WP promotes responsible disclosure by:

• Informing administrators and developers about risks.
• Providing actionable mitigation and detection guidance.
• Deploying managed protections to block live exploit attempts.

---

Risk evaluation and CVSS considerations

The vulnerability is rated “High” with a CVSS score that reflects its significant risk in typical WordPress environments.

• Exploitation requires user interaction by a privileged admin visiting attacker content.
• Privilege level of user affects the potential impact, which could range from moderate configuration changes to severe site compromise.
• Due to the plugin’s role in calendar synchronization, data exfiltration and persistence attacks are credible.

---

Immediate protective actions for site owners

Take these urgent steps if your site uses the WP-CalDav2ICS plugin:

1. Disable or deactivate the plugin until a patch is available or mitigations are applied.
2. Restrict admin dashboard access via IP whitelisting, VPN, or firewall rules to reduce exposure.
3. Educate site admins about avoiding untrusted links while logged into WordPress admin.
4. Perform a thorough site scan including malware checks, user account audits, and scheduled task reviews.
5. Rotate credentials linked with the plugin, such as API keys or tokens.
6. Enable or tighten WAF rules and virtual patching to block known malicious request patterns targeting affected endpoints.
7. Monitor access logs for unusual POST requests or unfamiliar admin access.

Follow the quick checklist: deactivate → educate → restrict → scan → rotate → patch → monitor.

---

Managed-WP mitigation services and recommendations

Managed-WP provides a layered defense approach:

1. Advanced Managed Web Application Firewall (WAF): Detects and blocks CSRF and related malicious request patterns targeting this plugin.
2. Virtual Patching: Rapid deployment of custom rules to protect your site even before official plugin fixes are released.
3. Origin and Referer enforcement: Adds an extra security layer to validate legitimate POST requests in the admin.
4. Automated malware scanning and remediation: Identifies suspicious changes and removes certain malware automatically (available in paid plans).
5. Rate limiting and access controls: Mitigates brute force or automated exploitation attempts.
6. Real-time visibility and alerting: Keeps you informed on suspicious traffic and admin access.
7. Expert guidance and support: Practical advice for both site owners and developers on remediation and prevention.

Managed-WP Basic Free Plan includes:

• Comprehensive WAF coverage against common threats including CSRF.
• Unlimited bandwidth with WAF protection.
• Malware scanning to detect signs of compromise.

For enhanced features such as auto virtual patching, malware removal, and proactive incident response, Managed-WP Premium plans are recommended.

---

Detection and investigation best practices

If you suspect compromise, proceed methodically:

1. Preserve logs and backups for offline forensic analysis.
2. Audit admin user accounts for unexpected additions or privilege escalations.
3. Check plugin files and settings for unauthorized modifications.
4. Review wp_options and cron jobs for suspicious changes.
5. Search for injected content or anomalies such as rogue posts or redirects.
6. Monitor access logs for unusual POST requests originating from untrusted sources.
7. Run comprehensive malware scans available via Managed-WP dashboards.
8. Rotate all affected credentials immediately.
9. Engage professional incident response if signs of compromise are confirmed or uncertain.

---

Recommended long-term fixes for developers and site managers

Plugin developers should:

1. Strictly validate nonces for all state-changing requests using check_admin_referer() or wp_verify_nonce().
2. Enforce capability checks via current_user_can() to confirm authorization.
3. Use POST rather than GET for actions modifying state.
4. Implement secure permission_callback functions on REST endpoints.
5. Sanitize and escape user inputs rigorously.
6. Include additional referer/origin checks for AJAX where appropriate.
7. Limit exposure of admin endpoints and document access policies clearly.
8. Employ automated tests that verify nonce presence and capability enforcement.

Managed-WP’s security team is available to assist plugin maintainers with reviews and virtual patching guidance.

---

Operational security best practices to reduce exposure

• Adopt least privilege principles for administrative accounts; use non-admin roles where feasible.
• Separate browsing profiles for admin tasks to minimize accidental exposure.
• Enforce multi-factor authentication (MFA) for all privileged users.
• Restrict admin access by IP or VPN where possible.
• Maintain regular, tested backups and recovery plans.
• Continuously monitor a vulnerability watchlist and retire or update unsupported plugins.

---

Free protection plan introduction

While following the guidance above, activate Managed-WP Basic (Free) Plan for an immediate security layer. It delivers managed firewall protection, WAF coverage focused on OWASP Top 10 risks, integrated malware scanning, and unlimited bandwidth. This baseline defense substantially reduces the chance of successful exploitation of plugin vulnerabilities.

Get started here: https://my.wp-firewall.com/buy/wp-firewall-free-plan/

---

Checklist: What to do now (quick reference)

• Deactivate WP-CalDav2ICS (≤ 1.3.4) if feasible until patches or mitigations exist.
• Notify admin users to avoid interacting with untrusted links while logged in.
• Apply or tighten WAF rules, including virtual patching for vulnerable endpoints.
• Run malware scans and audit user accounts for anomalies.
• Rotate API credentials and other secrets associated with the plugin.
• Enforce admin access restrictions by IP, VPN, or MFA.
• Monitor site logs for suspicious admin POST requests.
• Enroll in Managed-WP Basic Free Plan for immediate protection: https://my.wp-firewall.com/buy/wp-firewall-free-plan/

---

Appendix: commands and inspection tips for admins

Safe commands for site administrators — no exploit code included

• Identify recently modified files in the WP-CalDav2ICS plugin directory:
  find wp-content/plugins/wp-caldav2ics -type f -mtime -7 -ls
• Search web server logs for POST requests to the plugin’s endpoints:
  grep -i "wp-caldav2ics" /var/log/nginx/access.log | grep POST
• List recently created or modified admin users:
  In WP-Admin: Users → All Users → sort by registration date
  Or SQL query:
  SELECT ID,user_login,user_email,user_registered FROM wp_users ORDER BY user_registered DESC LIMIT 20;
• Review scheduled tasks (cron) for abnormalities:
  WP-Admin: Tools → Cron Events (with cron plugin)
  Or SQL query:
  SELECT option_value FROM wp_options WHERE option_name = 'cron';
• Query database for plugin-related settings:
  SELECT option_name, option_value FROM wp_options WHERE option_name LIKE '%caldav%' OR option_value LIKE '%caldav%';

---

Closing thoughts

This vulnerability highlights how third-party plugins, especially those integrating external services like CalDAV, can introduce critical attack surfaces if common security best practices are not followed. CSRF attacks are particularly dangerous because they exploit user trust and behavior, not just technical weaknesses.

Securing WordPress requires a multi-layered approach: solid plugin development hygiene (nonce and capability checks), operational controls (restricted access, MFA), and managed security defenses including WAF, virtual patching, and scanning.

Should you need assistance with implementing mitigations, incident response, or virtual patching, Managed-WP’s expert team is ready to support. Start immediately with our free protection to gain a robust baseline while you address the issue: https://my.wp-firewall.com/buy/wp-firewall-free-plan/

Stay vigilant, stay secure, and keep your plugins updated.

---

Take Proactive Action — Secure Your Site with Managed-WP

Don’t risk your business or reputation due to overlooked plugin flaws or weak permissions. Managed-WP provides robust Web Application Firewall (WAF) protection, tailored vulnerability response, and hands-on remediation for WordPress security that goes far beyond standard hosting services.

Exclusive Offer for Blog Readers: Access our MWPv1r1 protection plan—industry-grade security starting from just USD20/month.

• Automated virtual patching and advanced role-based traffic filtering
• Personalized onboarding and step-by-step site security checklist
• Real-time monitoring, incident alerts, and priority remediation support
• Actionable best-practice guides for secrets management and role hardening

Get Started Easily — Secure Your Site for USD20/month:
Protect My Site with Managed-WP MWPv1r1 Plan

Why trust Managed-WP?

• Immediate coverage against newly discovered plugin and theme vulnerabilities
• Custom WAF rules and instant virtual patching for high-risk scenarios
• Concierge onboarding, expert remediation, and best-practice advice whenever you need it

Don’t wait for the next security breach. Safeguard your WordPress site and reputation with Managed-WP—the choice for businesses serious about security.

Click above to start your protection today (MWPv1r1 plan, USD20/month). https://managed-wp.com/pricing