On 15 September 2025 a security advisory was published for The Events Calendar plugin (a widely used WordPress events plugin). The issue, recorded as CVE‑2025‑9808, affects versions up to and including 6.15.2 and is classified as Broken Access Control — specifically, a missing authorization check that can allow unauthenticated users to retrieve information that should have been protected by WordPress post passwords.

This advisory explains what the vulnerability means for your site, how to quickly determine whether you’re affected, practical and safe mitigations you can apply immediately, and long‑term recommendations to reduce risk from similar issues going forward. An official fix was released in The Events Calendar 6.15.3; updating is the recommended resolution. If you cannot update immediately, follow the mitigations below.

Executive summary (TL;DR)

• Vulnerability: Broken Access Control / Missing authorization for access to password‑protected event content.
• Impact: Unauthenticated attackers may be able to read content that site owners intended to protect with WordPress post passwords (events or event metadata).
• Affected versions: The Events Calendar ≤ 6.15.2.
• Fixed in: The Events Calendar 6.15.3 — update as soon as possible.
• CVSS score published: 5.3 (medium / low depending on context); required privilege: unauthenticated.
• Immediate actions: update the plugin; if you cannot, apply temporary server or application-level mitigations; audit logs for suspicious access to event API endpoints; rotate any exposed secrets if applicable.

Why this is serious — but not catastrophic

Password‑protected posts are a core WordPress feature to quickly restrict public access to specific posts or pages using a simple post password. Many site owners rely on that pattern to share events with a limited audience, or to hide draft/preview content.

A missing authorization check in a plugin that exposes event data — for example, via REST or AJAX endpoints — means a GET or POST request to an API endpoint could return content that should have required the post password. The attacker does not need to be logged in, and there is no required privilege. Disclosure can be silent and automated scanners can enumerate vulnerable sites at scale.

That said, this is an information disclosure issue rather than remote code execution. The primary risk is exposure of content (sensitive event details, attendee info if stored, notes, or internal links). In combination with other weaknesses (weak credentials, other vulnerable plugins, etc.), disclosed information can be useful to an attacker as a stepping stone.

How the vulnerability works (high level — no exploit details)

• The plugin exposes resources through public endpoints (REST API routes or admin‑ajax actions) that accept parameters identifying an event (post ID, slug, etc.).
• When a post is password‑protected, WordPress normally requires that the visitor submit the post password before the protected content is returned. That check is enforced by core template functions and by the post protection mechanisms.
• In this case, certain plugin endpoints returned protected fields (title, content, metadata) without verifying whether the caller had the correct post password or was otherwise authorized. In other words, an authorization guard was missing or bypassable in server side logic.
• Result: unauthenticated requests to specific endpoint(s) could receive data that should have been blocked by the post password protection.

No step‑by‑step exploit instructions will be published here; the remainder focuses on detection, mitigation, and response.

Am I affected? How to check quickly

1. Check your plugin version:
   • Login to WP Admin → Plugins, or inspect the plugin header in /wp-content/plugins/the-events-calendar/.
   • If The Events Calendar plugin version is 6.15.2 or lower, you are vulnerable. 6.15.3 contains the fix.
2. Look for evidence in access logs:
   • Search webserver or WAF logs for requests to event-related endpoints such as:
     • /wp-json/tribe/ or /wp-json/tribe/events/
     • /wp-admin/admin-ajax.php with action parameters referencing tribe or events
   • Search for repeated requests that include post IDs or slugs for password‑protected events.
3. Check whether you use password‑protected events:
   • If you use WordPress post passwords for events (Editor → Visibility → “Password Protected”), those entries are at risk.
4. Run a controlled test in staging:
   • Do not test exploitation against production. Use a staging copy with the same plugin version and controlled requests to see whether a REST endpoint returns protected content without authentication.

Immediate, responsible mitigation steps

If you host a site running The Events Calendar ≤ 6.15.2, prioritize the following in order:

1. Update the plugin to 6.15.3 (recommended)

The vendor issued a fix in 6.15.3. Updating removes the vulnerability entirely from your site. Test updates on staging first if you have customizations.

2. If you cannot update immediately, apply temporary mitigations

• Disable public API endpoints used by the plugin that might expose event content — for example, deregister or remove REST endpoints you do not need.
• Block access to specific URL patterns at the webserver or reverse proxy level:
  • Restrict paths such as /wp-json/tribe/* and /wp-admin/admin-ajax.php (filter requests with specific action names if feasible).
  • Rate‑limit requests to those endpoints to reduce large-scale scanning.
• Require authentication for sensitive endpoints — only allow requests that include a valid WordPress logged‑in cookie or a valid nonce header where appropriate.
• Temporarily set event posts you want private to “Private” rather than “Password protected” to require an account with publish rights. This is heavier but safer short term.
• Increase logging and alerting for REST and AJAX endpoint access so you can track and respond to suspicious requests quickly.

Practical temporary code mitigations (safe, defensive)

Below are sample defensive snippets you can use as temporary measures. Place these in a must‑use plugin (mu‑plugin) or theme functions on staging first, then carefully roll out to production. These are defensive and do not replace updating the plugin.

1) Disable REST endpoints exposing event data

<?php
/**
 * MU plugin: Disable The Events Calendar REST endpoints
 */

add_filter( 'rest_endpoints', function( $endpoints ) {
    foreach ( $endpoints as $route => $handlers ) {
        if ( strpos( $route, '/tribe/' ) !== false || strpos( $route, '/tribe/events' ) !== false ) {
            unset( $endpoints[ $route ] );
        }
    }
    return $endpoints;
});

Note: this is blunt and may break integrations that rely on those routes.

2) Enforce authentication for tribe REST requests

<?php
/**
 * MU plugin: Require authentication for select tribe endpoints
 */

add_action( 'rest_api_init', function() {
    $routes_to_guard = [
        '/tribe/events/v1/events',
        '/tribe/events/v1/events/(?P<id>[\d]+)',
        // add other route patterns you want to protect
    ];

    foreach ( $routes_to_guard as $route ) {
        register_rest_route( 'tribe/events/v1', $route, [
            'methods'             => 'GET',
            'permission_callback' => function() {
                return is_user_logged_in();
            },
            'callback'            => function() {
                return new WP_Error( 'rest_forbidden', 'You must be authenticated to access this endpoint', [ 'status' => 403 ] );
            },
        ] );
    }
}, 1 );

3) Block suspicious anonymous requests at server layer

Apache (.htaccess) example:

# Block direct access to tribe REST endpoints for non-logged-in users
<IfModule mod_rewrite.c>
 RewriteEngine On
 RewriteCond %{REQUEST_URI} ^/wp-json/tribe/ [NC]
 RewriteCond %{HTTP:Cookie} !wordpress_logged_in_ [NC]
 RewriteRule .* - [F]
</IfModule>

nginx example (server block):

location ~* ^/wp-json/tribe/ {
    if ($http_cookie !~* "wordpress_logged_in_") {
        return 403;
    }
}

These rules deny unauthenticated visitors from hitting plugin REST paths. Test carefully to avoid blocking legitimate traffic.

Virtual patch guidance (general)

If you manage a Web Application Firewall or reverse proxy with custom rule capability, create virtual patch rules that:

• Block or rate limit unauthenticated requests to REST endpoints that contain plugin-specific patterns such as /wp-json/tribe/ or admin-ajax requests with action=tribe*.
• Block requests that request full post content for password‑protected post IDs unless the request includes a WordPress logged‑in cookie or a valid nonce.
• Detect anomalous scanning behaviour (many requests for different post IDs in quick succession).

Example ModSecurity signature (illustrative; adapt and test):

SecRule REQUEST_URI "@beginsWith /wp-json/tribe/" "id:100001,phase:1,log,deny,status:403,msg:'Block possible Events Calendar unauthenticated REST access',chain"
  SecRule REQUEST_HEADERS:Cookie "!@contains wordpress_logged_in_" "t:none"

Always test WAF rules in staging; misconfigured rules can block legitimate services.

How to tell if your content was exposed (Indicators of Compromise)

• Access logs show unauthenticated GET/POST requests to /wp-json/tribe/ endpoints or to admin-ajax.php with action containing ‘tribe’ or ‘events’.
• Requests containing event post IDs corresponding to password‑protected posts.
• Spikes of requests to event routes from single IP ranges or known scanner infrastructure.
• Users report receiving event invites or participant lists they shouldn’t have seen.
• Unexpected copies of event content appearing on third‑party sites.

If you detect these, update immediately and treat the content as potentially disclosed. Notify affected parties if personal data was exposed and follow legal obligations.

If you believe you were compromised — incident response checklist

1. Immediately update The Events Calendar to 6.15.3.
2. Block the vulnerable endpoints (server or application rules) to stop further exposure.
3. Review access logs for the timeframe of potential exposure and collect logs for forensic review.
4. Identify which events/posts were password‑protected and consider those items compromised.
5. If attendee emails, phone numbers or other PII were stored and possibly exposed, follow your organisation’s breach notification procedures.
6. Rotate any relevant credentials (API keys, tokens) linked to event integrations.
7. Run full malware and file integrity scans to ensure no secondary compromise occurred.
8. Restore from a known clean backup if you find evidence of server compromise beyond data disclosure.
9. Harden monitoring and set up alerts for suspicious REST/AJAX activity going forward.

Long‑term security practices (reduce exposure to similar issues)

1. Maintain an inventory of plugins and themes; track versions and patch windows.
2. Enable automatic updates for security patches where safe.
3. Use a layered defence model: harden WordPress (strong passwords, 2FA for privileged users), keep server and PHP versions up to date.
4. Limit the use of public, unauthenticated APIs unless necessary.
5. Use staging sites for updates; test plugin updates for compatibility.
6. Log and monitor REST and admin‑ajax traffic, and alert on anomalous patterns.
7. Train content editors about data classification (what is sensitive and should not rely solely on post passwords).
8. Prefer role‑based access and private content features instead of post passwords for sensitive material.
9. Periodically audit plugins for security history and active maintenance.
10. Implement a vulnerability management process: track advisories for installed plugins and schedule patch windows.

Common questions from site owners

Q: If I update immediately, do I still need to do anything else?

A: Updating to 6.15.3 removes the specific bug. After updating, review logs for previous suspicious activity, run a full site scan, and ensure no other issues exist. If content may have been exposed, follow incident response steps.

Q: Are password‑protected posts still secure going forward?

A: Password protection is a convenience feature, not a substitute for access controls. For confidentiality, use private posts (require accounts with appropriate roles) or robust membership/authentication solutions.

Q: Will disabling REST endpoints break my site?

A: It depends. If you or integrations rely on plugin REST routes, disabling them may break functionality. Use server‑side blocking or rate limiting targeted at anonymous access as a lower impact alternative while testing.

Q: Can my site be fully protected without a WAF?

A: You can reduce exposure via updates, hardening, and webserver blocking; however, a WAF or reverse proxy with custom rule capability provides faster and more flexible mitigations during windows where updates cannot be applied immediately.

Technical detection rules for logging and SIEM

If you operate a SIEM or centralized logging, add these detection patterns:

• Alert on frequent hits to /wp-json/tribe/ from the same IP range.
• Alert on admin-ajax.php requests with action parameter containing tribe or events and no authenticated cookie.
• Alert on REST responses returning 200 with JSON containing post_content for known password‑protected post IDs.

Example Kibana/Elastic query:

(request.uri: "/wp-json/tribe/*" OR request.uri: "/wp-admin/admin-ajax.php") AND NOT request.headers.cookie:/wordpress_logged_in_/

Final recommendations (step-by-step)

1. Verify plugin version now.
2. If you run The Events Calendar ≤ 6.15.2, upgrade to 6.15.3 as soon as possible.
3. If you cannot upgrade immediately:
   • Implement server rules blocking unauthenticated access to tribe REST routes.
   • Consider temporarily disabling REST endpoints as shown in the defensive snippets.
   • Increase logging and monitoring of event endpoints.
4. Audit any password‑protected events for sensitive content and assume exposed until proven otherwise.
5. Follow the incident response checklist if you find evidence of access.
6. Implement the long‑term practices described above and add vulnerability monitoring to your update process.

Closing thoughts

Information disclosure vulnerabilities are often underestimated because they do not immediately lead to account takeover or remote code execution. However, exposing private event details, attendee lists, or internal links can cause reputational harm, leaked PII, or targeted follow‑on attacks.

A layered approach — timely updates, responsible staging and testing, careful use of WordPress privacy features, and the ability to deploy reversible virtual patches at the server or proxy layer — provides the best protection with the least disruption.

If you need an assessment or implementation assistance, consult a trusted local security professional to help with detection, temporary mitigations, and safe deployment of the fixed plugin version.