Critical: The Events Calendar (v6.15.1.1–6.15.9) — Unauthenticated SQL Injection (CVE-2025-12197)

As security practitioners based in Hong Kong, we present a clear, practical advisory for site owners, developers and operations teams about the recently disclosed unauthenticated SQL injection in The Events Calendar plugin (versions 6.15.1.1 through 6.15.9), tracked as CVE-2025-12197. This post explains the impact, how attackers may exploit it, how to detect signs of compromise, immediate mitigation steps, developer fixes, and an incident-response checklist you can run on affected sites.

Important facts at a glance

• Vulnerability: Unauthenticated SQL Injection
• Affected versions: The Events Calendar plugin 6.15.1.1 — 6.15.9
• Fixed in: 6.15.10
• CVE: CVE-2025-12197
• Required privilege: none (unauthenticated)
• Reported: 5 November 2025
• Risk: High — CVSS 9.3

Why this matters (plain language)

An unauthenticated SQL injection allows an attacker on the public internet to send requests that influence SQL queries executed by the plugin without needing to log in. This can permit reading, modifying or deleting database content: user emails, password hashes, private metadata, creation of privileged accounts, installation of backdoors, or full site compromise. Because the flaw is unauthenticated and The Events Calendar is widely used, the potential for rapid mass exploitation is significant.

Operators should treat this as urgent. If you run The Events Calendar and cannot update immediately, apply mitigations as a priority.

What probably went wrong (technical overview — for developers)

Common causes for this class of vulnerability in WordPress plugins include:

• User-supplied input (query parameters used for searches or filters) is concatenated into SQL or passed into WP_Query without proper sanitisation or parameterisation.
• A public parameter (often s or similar) is used in a raw query or format string and not prepared via $wpdb->prepare(). Input containing SQL metacharacters (quotes, comment tokens, UNION/SELECT, etc.) can then alter query structure.
• Unauthenticated endpoints (public REST endpoints, admin-ajax front-end handlers, or front-end query parameters) allow any remote actor to trigger the vulnerable code path.

Developer takeaways:

• Never build SQL by concatenating raw user input.
• Use $wpdb->prepare() for custom SQL queries.
• Prefer WP_Query with sanitized arguments.
• When creating REST endpoints, validate and sanitise all parameters strictly.

Example (safe patterns)

Prepared statement with $wpdb:

<?php
global $wpdb;
$sql = $wpdb->prepare( "SELECT * FROM {$wpdb->prefix}events WHERE slug = %s", $slug );
$rows = $wpdb->get_results( $sql );
?>

Using WP_Query safely:

<?php
$args = array(
  'post_type' => 'tribe_events',
  's' => sanitize_text_field( $_GET['s'] ?? '' ),
  'posts_per_page' => 10,
);
$query = new WP_Query( $args );
?>

If your theme or plugin passes raw $_GET / $_REQUEST values into SQL or WP_Query without sanitisation and validation, patch it now.

Immediate mitigation steps for site owners (priority checklist)

1. Update the plugin. The simplest and most reliable fix is to update The Events Calendar to version 6.15.10 or later as soon as possible.
2. If you cannot update immediately:
   • Apply protective controls quickly. If you run a Web Application Firewall (WAF) or have access to request-filtering at the edge, configure rules to block the attack patterns described below.
   • Temporarily disable the plugin if your site can operate without it until you can update.
3. Restrict access to relevant endpoints. Block or restrict public access to endpoints that handle event searches, filters or AJAX calls if they are not required. Limit REST and admin-ajax access by IP allowlisting, authentication, or rate limiting.
4. Tighten web server rules. Add server-level request filtering to reject suspicious payloads in query strings or POST bodies.
5. Monitor logs and scan. Enable detailed logging and scan for the Indicators of Compromise (IoCs) listed below.
6. Rotate credentials after investigation. If you find signs of compromise, rotate database credentials, all administrator passwords and WordPress salts/keys after preserving forensic data.

Detecting exploitation — Indicators of Compromise (IoCs)

Look for these signs when hunting for exploitation:

• Suspicious HTTP requests: Requests with s= or other params containing SQL keywords (UNION, SELECT, INFORMATION_SCHEMA, GROUP_CONCAT, BENCHMARK, SLEEP, comment tokens like --, #, /*), hex-encoded payloads or long encoded strings. Rapid repeated requests to the same endpoint are indicative of scanning or exploitation attempts.
• New or altered admin users: Inspect wp_users and wp_usermeta for unexpected admin-level accounts or capability changes.
• Modified files: Unexpected edits to core, theme or plugin files. Look for base64_decode(), eval(), unusual includes, or PHP files placed in wp-content/uploads.
• Strange scheduled tasks: Malicious entries in the cron option or unknown scheduled jobs.
• Unexpected posts/options: Posts with zero-length content, injected payloads, or strange option values.
• Database anomalies: Unexpected rows in options, posts, comments or usermeta containing long or encoded strings.

Example read-only SQL queries for hunting (run on a copy where possible):

-- Find recent user registrations
SELECT ID, user_login, user_email, user_registered FROM wp_users ORDER BY user_registered DESC LIMIT 20;

-- Inspect options for serialized entries with "cron" or "eval("
SELECT option_name, option_value FROM wp_options WHERE option_name LIKE '%cron%' OR option_value LIKE '%eval(%' LIMIT 20;

-- Search posts for suspicious content
SELECT ID, post_title FROM wp_posts WHERE post_content LIKE '%base64_%' OR post_content LIKE '%eval(%' LIMIT 50;

Incident response: if you find evidence of compromise

If IoCs indicate compromise, assume the site is affected and act methodically:

1. Take the site offline or into maintenance mode to prevent further damage.
2. Preserve forensic data: copy web and application logs, export the database, and take a filesystem snapshot.
3. Change passwords and rotate database credentials, but only after preserving evidence.
4. Restore from a known-clean backup if available and verified.
5. If no clean backup exists, rebuild from scratch: export content, thoroughly scan and clean it, reinstall core/themes/plugins from official sources, and re-import cleaned content.
6. Scan the restored site with multiple tools and enable file integrity monitoring.
7. Harden configuration and closely monitor logs for re-infection.
8. If uncertain, engage experienced incident response professionals to perform forensic analysis and remediation.

Virtual patching and WAF guidance (practical — mitigation now)

Virtual patching (applying targeted request-filtering rules at the edge or WAF) is a temporary measure — not a replacement for updating. If you have a WAF or edge filtering capability, implement context-aware rules that target likely exploit patterns rather than broad keyword blocks that will break legitimate searches.

Effective rule characteristics:

• Block SQL injection patterns in query parameters relevant to The Events Calendar (e.g., search param s or other filter parameters). Focus on combinations such as SQL keywords plus special characters (e.g., union+select, information_schema, group_concat).
• Use positive (whitelist) validation for endpoints that accept limited input types: enforce length limits, allowed characters and types.
• Rate-limit or throttle requests to endpoints under heavy automated access to reduce exploitation speed.
• Block overly long or base64-encoded query strings that are unlikely to be legitimate search terms.
• Log and alert on matched patterns so you can review and refine rules to reduce false positives.

Conceptual rule example (not exact WAF syntax):

If request path matches /events/* or /wp-admin/admin-ajax.php AND query param s matches regex (case-insensitive): \b(union|select|information_schema|group_concat|benchmark|sleep)\b|(--|#|/\*) THEN block and alert.

Important: blunt keyword blocking may break legitimate content. Tune rules for length, charset and context to avoid damaging user experience.

How to tune WAF protections for this issue

When configuring WAF/edge rules, apply a layered approach:

• Deploy targeted rules quickly to intercept known attack vectors without disrupting normal search behavior.
• Use behavioural detection to identify scanning or burst patterns (many requests from multiple IPs targeting the same endpoint).
• Scan historical logs once protections are active to detect past successful injections.
• Alert site operators promptly about notable blocks or suspected exploit attempts.
• When the official plugin update is applied, remove temporary rules that negatively affect functionality and rely on the code fix.

Long-term fixes for plugin authors (developer checklist)

• Principle of least privilege: ensure public endpoints do not expose admin-level functionality.
• Sanitise and validate every input: use filter_input(), sanitize_text_field(), wp_parse_args() and explicit type checks.
• Use parameterised queries: $wpdb->prepare() for custom SQL.
• Prefer WordPress APIs: use WP_Query, get_posts() and other abstractions rather than raw SQL where possible.
• Implement unit and fuzz tests that exercise public endpoints with both benign and malicious input.
• Log suspicious input for later review and tuning.
• Conduct regular security reviews and dependency checks.

Operational hardening checklist (for site owners)

• Keep WordPress core, plugins and themes up to date.
• Use strong, unique admin passwords and enforce MFA for administrators.
• Minimise admin user count and audit roles frequently.
• Use least-permission SFTP/FTP accounts and avoid exposing credentials.
• Maintain offline versioned backups and test restores regularly.
• Enable file integrity monitoring to detect unauthorised changes.
• Run regular malware and database integrity scans.
• Centralise logs (web, application, DB) and monitor them for anomalies.
• Use restricted database users — avoid high-privilege DB accounts for the app.
• Rotate salts and security keys if you suspect credential theft.

Testing and verification after remediation

After updating the plugin and/or applying temporary protections, verify the following:

• The plugin is updated to version 6.15.10 or later.
• WAF or edge rules are not blocking legitimate site functionality (search, filters, event listings).
• Logs show no successful exploitation attempts and recent blocked attempts are recorded for review.
• Rescan site for malware and indicators of prior compromise.
• Confirm admin users and file modification times for unexpected edits.
• If a backup was used to restore, validate the restored site’s functionality and monitor closely for re-infection.

What attacks could look like (high-level — no exploit details)

Typical exploitation scenarios:

• An attacker sends a crafted GET or POST request to a public events endpoint including a malicious s or filter parameter. If the plugin uses that parameter unsafely in SQL, the attacker can exfiltrate data or write to the database (including adding admin accounts via usermeta/options).
• Automated scanners will probe many sites and inject payloads automatically; the unauthenticated nature makes low-effort mass exploitation likely.

Frequently asked questions (FAQ)

Q: I updated — am I safe?
A: If you updated The Events Calendar to 6.15.10 or later, the vendor fix addresses this specific vulnerability. Continue to follow the detection checklist to ensure the site was not already compromised.

Q: I can’t update because of customisations — what should I do?
A: If update is not immediately feasible, apply temporary protections: restrict access to vulnerable endpoints, implement tight request filtering or WAF rules, and schedule work to update or safely merge your customisations so you can upgrade.

Q: Is virtual patching sufficient forever?
A: No. Virtual patching or WAF rules are a temporary bridge to block exploitation while you plan and implement the official code fix. Always update to the official patched version when possible.

Q: I found suspicious activity — should I restore a backup?
A: If you have a trusted clean backup from before the suspected compromise, restoring can be the fastest remediation. Preserve forensic evidence first, then restore and rotate credentials after the restore.

Final recommendations (clear, practical)

1. Update The Events Calendar plugin to v6.15.10 immediately.
2. If you cannot update immediately, apply temporary protections: narrow WAF/request-filtering rules, restrict access to endpoints, or disable the plugin if feasible.
3. Hunt and scan logs for Indicators of Compromise; treat any positive finding as a potential compromise and follow the incident-response checklist.
4. Harden site configuration: reduce access, enable MFA, rotate keys and credentials after incidents, and keep tested backups offline.
5. For developers: adopt parameterised queries, sanitise every input, and favour core APIs rather than raw SQL.

If you need specialist incident response or forensic investigation, engage professional responders with WordPress and database forensic experience. Prompt, correct action reduces the chance of reinfection and limits damage.

Stay vigilant — unauthenticated SQL injection is a high-impact issue but with timely updates and careful mitigation you can protect your sites.