プラグイン名	The Events Calendar
Type of Vulnerability	SQLインジェクション
CVE Number	CVE-2025-9807
緊急	高い
CVE Publish Date	2025-09-11
Source URL	CVE-2025-9807

Urgent: The Events Calendar (<= 6.15.1) — Unauthenticated SQL Injection (CVE-2025-9807) — What WordPress Site Owners Must Do Now

公開日: 11 September 2025
著者： WP-Firewall Security Team

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まとめ

• Software affected: The Events Calendar (WordPress plugin)
• Vulnerable versions: ≤ 6.15.1
• Fixed in: 6.15.1.1
• CVE: CVE-2025-9807
• Required privilege: Unauthenticated (no login required)
• Severity: High — CVSS 9.3
• Primary risk: Unauthenticated SQL injection leading to database disclosure, modification, or remote code execution when chained with other weaknesses

If your site uses The Events Calendar plugin and the plugin version is 6.15.1 or older, treat this as an emergency. An unauthenticated SQL injection in a widely used plugin means attackers can target your site without credentials and directly interact with your database. Below we explain the vulnerability impact, safe detection methods, practical mitigations, long-term hardening steps, and how a managed WAF + virtual patching strategy can protect sites that cannot be updated immediately.

NOTE: Do not delay — update the plugin to 6.15.1.1 or later as your primary mitigation. Read on for compensating controls and incident-response guidance.

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Table of contents

1. What happened (plain language)
2. Why this is dangerous (impact)
3. High-level technical explanation (what to look for)
4. How attackers may exploit this (risk scenarios)
5. Detecting compromise and indicators of attack
6. Immediate actions for site owners
7. Virtual patching and WAF-based mitigations (how WP-Firewall helps)
8. Example WAF rule patterns (safe, non-exploit proofing)
9. Incident response and recovery checklist
10. Post-incident hardening and best practices
11. Protect your site today — WP-Firewall Free Plan

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1) What happened (plain language)

A critical SQL injection vulnerability was discovered in The Events Calendar plugin for WordPress that allows unauthenticated visitors to inject SQL into database queries handled by the plugin. Because the flaw requires no authentication, attackers can attempt to exploit it simply by sending specially crafted HTTP requests to endpoints provided by the plugin.

In short, an attacker could read or modify information in your WordPress database (posts, users, meta, event data), create or elevate user privileges, or pivot to achieve remote code execution depending on your environment and other installed software.

2) Why this is dangerous (impact)

• Unauthenticated: No account required to trigger the vulnerability. Remote actors on the internet can target your site.
• Database-level control: Successful SQL injection can leak sensitive data (emails, passwords in hashed form, API keys, event/location details) and may permit destructive changes.
• Mass exploitation potential: Widely used plugins with unauthenticated flaws are common early targets for automated scanners and botnets; this can lead to rapid, large-scale compromise.
• Chainability: SQLi can be combined with stored XSS, plugin-specific file-write bugs, or poorly-protected admin endpoints to achieve full site takeover.
• Reputation, compliance, and data exposure costs: Data theft or site defacement can cause prolonged downtime, regulatory exposure, and loss of customer trust.

3) High-level technical explanation (what to look for)

While specific implementation details are part of the vendor’s disclosure and patch notes, the core issue is insufficient input handling in a query constructed by the plugin. Common root causes for this class of issue include:

• Direct concatenation of user-controlled data into SQL statements without using parameterized queries / prepared statements.
• Failure to validate input types and allowed characters before including them in SQL statements.
• Server-side endpoints (REST API, admin-ajax, or custom endpoint) that accept parameters and pass them into wpdb->get_results() or similar without sanitization.

Where to inspect:

• The plugin’s REST endpoints and AJAX handlers.
• Any code paths that build SQL conditions dynamically from GET/POST parameters.
• Changelog or release notes from the plugin author for the exact patched functions.

We do NOT publish proof-of-concept exploit code here — exposing step-by-step exploitable payloads for an actively exploitable, unauthenticated vulnerability would put more sites at risk. If you are performing authorized security testing on your own site, limit tests to non-production copies or schedule maintenance windows.

4) How attackers may exploit this (risk scenarios)

Typical exploitation vectors that attackers use in the wild:

• Automated scanning bots: Inventory sites with The Events Calendar and probe known endpoints to see whether the plugin responds in expected ways, then attempt injection patterns.
• Data exfiltration: Use boolean or error-based SQLi techniques to retrieve sensitive fields such as user email addresses or hashed passwords.
• Stored payload placement: Inject content into event descriptions or other database fields that then becomes active in the frontend (combined with XSS).
• Privilege escalation: Modify wp_users or usermeta tables to insert or elevate admin accounts.
• Lateral movement: Drop backdoor files if the attacker can use DB writes to influence code or trigger functionality that allows writing to the filesystem.

Because this is unauthenticated, the window for automated mass-scanning and subsequent exploitation is measured in hours-to-days following public disclosure. Do not assume your site will be spared.

5) Detecting compromise and indicators of attack

Look for the following signs in your logs and database that may indicate attempted or successful exploitation:

Web server / application logs:

• Unusual request spikes to plugin endpoints (URLs under the plugin namespace or REST routes added by the plugin).
• Requests containing SQL keywords in query strings or POST bodies (e.g., SELECT, UNION, –, OR 1=1).
• Requests from high-volume IPs or IPs with failed/repeated attempts followed by successful requests.

Database and application indicators:

• Unexpected changes in wp_posts, wp_postmeta, wp_users, wp_usermeta, or custom tables used by the plugin.
• Strange admin users created recently, especially with weak or blank passwords (attackers sometimes create accounts and then change auth data).
• Event records with unusual content (injected SQL fragments or encoded payloads).
• Errors in error logs that reveal SQL syntax errors or stack traces from plugin functions.

Filesystem signs:

• New PHP files in wp-content/uploads, wp-content/plugins, or other writable directories.
• Modifications to wp-config.php or theme files, though those are more likely when other write holes exist.

Recommended log searches (examples you can run safely):

• Search your web server access log for requests hitting the plugin’s endpoints.
• Use grep or your logging platform to detect SQL-related tokens in requests: SELECT, UNION, SLEEP(, BENCHMARK(, –, /*, @@, information_schema.
• Inspect DB audit logs (if present) for odd queries at times you didn’t perform maintenance.

6) Immediate actions for site owners (ordered, practical)

If your site runs The Events Calendar ≤ 6.15.1, follow these immediate steps:

1. Patch first
   • Update The Events Calendar plugin to 6.15.1.1 or later as soon as possible. This is the single most effective measure.
   • If you use automatic updates, verify the plugin was updated successfully and clear caches.
2. If you cannot update immediately, mitigate with runtime protections
   • Enable a managed Web Application Firewall (WAF) or apply virtual patching rules that block known exploitation patterns for this vulnerability.
   • Restrict access to plugin endpoints using IP allowlisting where feasible (e.g., if administrative calls only come from specific networks).
   • Disable public-facing endpoints of the plugin if you are not using them (some plugins allow turning off REST support).
3. Monitor logs aggressively
   • Watch web server access logs and WAF logs for probing attempts and the indicators listed above.
   • Temporarily increase alerting sensitivity for suspicious requests toward plugin endpoints.
4. Take a backup
   • Create a fresh file + database backup immediately (store off-site).
   • If you suspect compromise, take a snapshot before making changes for later forensic review.
5. Scan and clean
   • Run a malware scan and code integrity checks.
   • If suspicious files are found or DB changes detected, follow an incident response process (see section 9).

7) Virtual patching and WAF-based mitigations (how WP-Firewall helps)

If you cannot update immediately (e.g., customizations that require testing), virtual patching via a WAF is a robust compensating control:

What virtual patching does

• Blocks malicious requests before they reach the vulnerable code path.
• Applies rules that detect and drop SQL injection payloads targeted at known plugin endpoints.
• Prevents large-scale automated exploitation while you plan and perform a safe update.

Why managed WAFs are useful here

• Rapid deployment: A WAF rule can be created and applied in minutes, protecting thousands of sites that share the same plugin vulnerability.
• Continuous updates: Rules are tuned and refined to reduce false positives while covering new variants attackers attempt.
• Logging and forensics: WAFs provide detailed logs and can be used to identify blocked attempts and the actors behind them.

WP-Firewall approach (how we protect customers)

• Immediate rule rollout: We develop and distribute rules that block the signature behaviors associated with this SQLi without relying on fragile pattern matches.
• Virtual patch for sites that cannot update immediately: Our virtual patch isolates the vulnerable endpoint and prevents suspicious payloads from reaching query-building code.
• Monitoring and notification: Customers receive alerts for blocked exploits, along with recommended remedial steps and timeline for updating.
• Complementary protections: Managed malware scanning and post-exploit detection to identify IOCs that may indicate a successful bypass attempt.

8) Example WAF rule patterns (safe, non-exploit proofing)

Below are safe, high-level rule patterns and approaches WAF engineers commonly use to reduce exposure to SQLi in plugin endpoints. These are conceptual and should be adapted and tested for your environment to prevent false positives.

• Block requests to known plugin endpoints if not required
  If the plugin exposes an API path like /wp-json/tribe/events/v1/* (example), consider returning 403 to requests from countries/IP ranges you don’t serve or to unauthenticated traffic where allowed.
• Parameter validation and whitelisting
  Enforce allowed character classes and length restrictions for parameters accepted by the plugin (e.g., slugs, page numbers, filter names). Reject or challenge parameters containing SQL metacharacters.
• Generic SQLi pattern block (non-exhaustive)
  Detect high-risk tokens in user-supplied parameters and block or hold-for-review:
  • Tokens: “UNION”, “SELECT”, “INSERT”, “DROP”, “SLEEP(“, “BENCHMARK(“, “–“, “/*”, “*/”, “information_schema”
  • Reject requests that include these tokens in parameters that should never contain them (IDs, slugs, sort keys).
• Anomaly scoring and rate limits
  Rate-limit requests to plugin endpoints and apply anomaly scoring; if a client exceeds thresholds or exhibits high-risk token use, block for a cooling-off period.
• Content-length and encoding checks
  Monitor for percent-encoded SQL payloads or excessive URL-encoded payload size that can indicate attempts to obfuscate injected SQL.

Sample (pseudocode) WAF rule — conceptual only:

IF request.path STARTS_WITH "/wp-json/tribe/events" AND request.auth IS NULL THEN
  IF request.query_params CONTAINS_REGEX "(?i)(union|select|information_schema|benchmark|sleep)\b" THEN
     BLOCK request WITH 403
  ENDIF
  IF request.query_params['id'] NOT MATCH "^\d{1,6}$" THEN
     BLOCK request WITH 403
  ENDIF
ENDIF

Important: Test any rule on staging before deploying to production. Overly broad rules can break legitimate plugin functionality. Managed WAF providers (like the WP-Firewall team) tune rules to balance security and functionality for common plugin usages.

9) Incident response and recovery checklist

If you suspect exploitation or find suspicious artifacts, follow this prioritized checklist:

A. Containment

• Apply WAF rule or temporarily disable the plugin endpoints.
• Temporarily set site to maintenance mode if necessary to prevent further exposure.

B. Evidence preservation

• Create snapshots of the server and database.
• Export logs (web server, application, WAF) for the relevant time window.

C. Analysis

• Review access logs for suspicious requests and timeline.
• Inspect database for unauthorized changes: newly created users, changed capabilities, modified posts/events.
• Scan filesystem for unknown PHP files or recently modified files.

D. Remediation

• Update plugin to patched version (6.15.1.1 or later).
• Remove unauthorized users and reset passwords for administrator accounts.
• Restore files from clean backups if file tampering is confirmed.
• Rotate credentials that may have been exposed: API keys, database passwords, external service tokens.

E. Post-incident hardening

• Re-run malware and rootkit scanners.
• Implement multi-factor authentication for all admin users.
• Strengthen logging and alerting thresholds to detect similar future activity earlier.

F. Communication

• If data was exposed (personal data, payment-related info), follow applicable breach notification laws and inform stakeholders and hosting provider.
• Document timeline and actions taken for internal and regulatory purposes.

10) Post-incident hardening and best practices

Use this incident as a prompt to reinforce your overall WordPress security posture:

• Keep plugins and WordPress core updated. Apply updates to staging first if you need to test customizations.
• Reduce plugin footprint: deactivate and remove plugins you do not actively use.
• Run principle of least privilege: reduce admin users and use role-based access controls.
• Enforce strong passwords and enable multi-factor authentication (MFA) for all privileged accounts.
• Use a managed WAF with virtual patching capability as part of your layered defense-in-depth.
• Schedule regular backups with off-site retention and periodic restore tests.
• Implement file integrity monitoring to detect unauthorized code changes quickly.
• Use an account access log and alert on new admin account creation.
• Segment hosting environments and restrict database access to only what’s necessary.

11) Protect your site today — WP-Firewall Free Plan

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Plan summary (at-a-glance)

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Why this matters

• Free protection reduces exploit surface and blocks automated attacks so you can patch safely.
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Closing notes from WP-Firewall Security Team

This SQL injection vulnerability is a serious, time-sensitive issue because it is exploitable without authentication and affects a widely used event management plugin. The single best action is to update the plugin to the fixed version immediately. Where immediate updates are not possible, use virtual patching via a managed WAF and follow the incident-response steps above.

Our team is actively monitoring for exploitation attempts and continuously updating rule sets to protect our customers. If you need help triaging suspicious activity, implementing temporary mitigations, or orchestrating a clean recovery, reach out to your hosting provider or a qualified WordPress incident response service.

Stay safe, keep backups, and patch early.

— WP-Firewall Security Team

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References & further reading

• Official plugin changelog and vendor advisory (check the plugin page or vendor support for the precise patched files and guidance).
• CVE details: CVE-2025-9807 (reference page).
• OWASP guidance on SQL Injection and web application testing.

(If you use this post in an environment where you perform active testing, please always work on a staging copy and get proper authorization for security testing.)