プラグイン名	User Extra Fields
Type of Vulnerability	Arbitrary File Deletion
CVE Number	CVE-2025-7846
緊急	高い
CVE Publish Date	2025-10-31
Source URL	CVE-2025-7846

Urgent: WordPress User Extra Fields (<= 16.7) — Authenticated Subscriber Arbitrary File Deletion (CVE-2025-7846)

まとめ

• Severity: High (CVSS: 7.7)
• Vulnerable versions: <= 16.7
• Fixed in: 16.8
• Required privilege: Subscriber (authenticated)
• Vulnerability type: Arbitrary file deletion via plugin endpoint (save_fields)
• Reported by: security researcher (credit: Tonn)
• Published: 31 October 2025

If your site uses the User Extra Fields plugin, this vulnerability should be treated as urgent. An authenticated user with Subscriber-level access can trigger a function in the plugin (save_fields) that results in arbitrary deletion of files. Impact includes site breakage, loss of media or code, partial or complete defacement, and the potential for attacker pivot if combined with other weaknesses. Update to the patched version (16.8) immediately; if you cannot update right now, implement the mitigations below.

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Why this matters — plain language

A Subscriber account is the lowest privileged account on many WordPress sites. On its own a subscriber shouldn’t be able to change files on the server. This flaw effectively allows such low-privileged users to delete files — including plugin, theme, or core files — if the plugin is exposed in a way that allows them to call the vulnerable save_fields functionality.

An attacker who can delete critical files can:

• Break the site (missing files produce 500/404 errors).
• Remove security controls or logs.
• Remove files to cover tracks.
• Combine deletion with other vulnerabilities to gain further control.

Because the vulnerability is exploitable by a user with only a Subscriber role, it dramatically lowers the bar for attack and can be scaled automatically across compromised or malicious user accounts (for example, on sites that allow user registration).

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Technical overview (high-level, non-exploitable detail)

• The plugin exposes a function (save_fields) that processes user input and performs file operations.
• Input used by this function is not sufficiently validated or restricted, allowing crafted input to reference files outside safe, intended directories.
• There is insufficient capability/permission checking around that operation — a Subscriber can reach the codepath that invokes deletion.
• The result: arbitrary file deletion with the privileges of the web server user.

Note: Responsible disclosure conventions were followed by the reporter and a patch is available in version 16.8. Public exploit details are being kept minimal here to avoid giving attackers a “playbook”.

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What can be deleted? Realistic worst-case scenarios

An attacker could delete:

• Files in the uploads directory (images, documents) — causing user content loss.
• Theme or plugin files — breaking site layout/functionality and possibly disabling security plugins.
• Files in plugin directories, potentially disabling protection or enabling further tampering.
• Configuration or bootstrapping files if the web server permissions are broad (e.g., wp-config.php in poorly configured setups).
• Log files — making investigation and recovery more difficult.

The exact risk depends on webserver file permissions, ownership, and the hosting environment. On many shared hosts, the webserver user owns plugin/theme files and therefore deletions can be destructive.

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Attack vectors and scenarios

1. Malicious registered user:
   • A site with open registration allows attackers to create Subscriber accounts. They can then call the vulnerable endpoint to delete files.
2. Compromised subscriber account:
   • A real user’s account is compromised (weak password, reuse) and the attacker uses it to delete files.
3. Malicious plugin or theme integration:
   • If another plugin or theme interacts with the vulnerable function (via hooks or AJAX), that could be used to trigger deletions.
4. Chained attack:
   • Delete key plugin/theme files, then upload malicious code through an unprotected upload path or exploit another vulnerability. Deletion can be used to lower defenses or pivot.

Because the required privilege is low, these are straightforward to automate at scale against multiple sites.

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Indicators of Compromise (IoC) — what to look for now

If you suspect this plugin or any file deletion attack, look for:

• Unexpected 404/500 errors on pages that previously worked.
• Missing media items in Media Library (thumbnails or full-res).
• Missing files in wp-content/plugins/<plugin-name>/ または wp-content/themes/<theme>/.
• Unusual POST requests to 管理者-ajax.php, REST endpoints, or plugin-specific endpoints where Subscribers can reach.
• Server or application logs showing POST/GET to plugin endpoints from authenticated subscriber users.
• Sudden gaps in logging (deleted logs), or logs showing file operations initiated by the plugin.
• File system integrity alerts if you have file integrity monitoring (FIM) in place.
• Alerts from your hosting provider that files were removed or permissions changed.

Collect logs immediately. Network and PHP access logs plus MySQL logs (if relevant) are helpful. Preserve evidence before restoring.

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Immediate actions (if the plugin is installed)

1. Check plugin version
   • From WordPress Dashboard -> Plugins -> Installed Plugins, verify User Extra Fields version. If it is <= 16.7, treat as vulnerable.
2. Update immediately
   • Update the plugin to 16.8 or later. This is the simplest and most reliable fix.
3. If you cannot update right away:
   1. Restrict access to the plugin endpoint.
      • Block requests to any known plugin actions from unauthorised roles.
   2. プラグインを一時的に無効にする
      • Deactivate the plugin in the Dashboard (Plugins -> Deactivate).
      • If Dashboard access is not available, rename the plugin folder via SFTP or hosting file manager (e.g., change wp-user-extra-fields に wp-user-extra-fields-disabled).
   3. Harden user registration and accounts
      • Disable user registration if not needed.
      • Force password resets for users with Subscriber role if suspicious.
   4. Apply WAF rules / virtual patch (examples below)
   5. Tighten file permissions
      • Ensure wp-config.php is 440/400 where the environment allows.
      • Ensure plugin/theme files are not writable by the world (chmod 644 for files, 755 for directories; owner should be the deployment user where possible).
4. Check for evidence of exploitation
   • Inspect logs for suspicious activity from Subscriber accounts.
   • Check for missing files in uploads, plugins, and themes.
   • If files are missing, preserve a copy of the current filesystem before restoring from backup.
5. Restore from a clean backup (if needed)
   • If critical files were deleted and you have a clean backup, restore those files.
   • After restoring, update plugin to 16.8 before re-activating.
6. Post-remediation
   • Rotate any exposed secrets (API keys, access tokens).
   • Review user accounts and remove unknown ones.
   • Re-scan for malware.

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WAF / Virtual patching recommendations (generic rules you can apply now)

If you operate a web application firewall (WAF) — or a host-managed firewall — you can create virtual rules to block exploit attempts until updating is possible. The following are generic examples and must be tuned to your environment. Do not enable wild, overly broad rules without testing; you may block legitimate traffic.

1. Block calls to the vulnerable action or endpoint from subscriber users
   • If the plugin exposes an AJAX or REST action name (e.g., save_fields), block requests that include that action when the requestor is not a admin/editor.
   • Example pseudo-rule:
     • If request contains parameter action=save_fields and request is a POST to 管理者-ajax.php, then block.
2. Block suspicious path traversal patterns
   • Deny requests with parameters containing ../ or absolute paths that reference wpコンテンツ, wp-includesなど
   • Example regex to detect path traversal:
     • (\.\./|\.\.\\|/etc/passwd|[A-Za-z]:\\) (tune as needed)
3. Block requests that attempt file operations
   • If any parameter is attempting to delete or modify files (e.g., contains keywords like unlink, delete, rm in unexpected parameters), block or alert.
4. Rate-limit authenticated subscriber accounts
   • Limit number of POST requests to 管理者-ajax.php or the REST endpoint from Subscriber accounts per minute. This slows automated mass exploitation.
5. Monitor and alert
   • Create an alert rule: any blocked attempt matching the above patterns should notify administrators immediately.

Example ModSecurity-style rule (illustrative only — adapt for your WAF engine):

# Block POST to admin-ajax.php with action=save_fields
SecRule REQUEST_METHOD "POST" "phase:2,chain,deny,status:403,id:1000001,msg:'Block save_fields exploitation attempt'"
  SecRule ARGS_NAMES|ARGS|REQUEST_URI "@rx (action=save_fields|save_fields)" "t:none,t:lowercase,ctl:auditLogParts=+E"

Do not publish exact exploit payloads. The goal is to prevent attack attempts, not to reproduce them.

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How to update safely (best practice)

1. Test on staging
   • Always apply plugin updates on a staging site before production.
   • Useful checks: site functionality, site frontend and backend, key flows like login, checkout (if e-commerce), custom code that calls plugin hooks.
2. Back up first
   • Make a full site backup (files + database) before updating. Prefer automated backup solutions with retention.
3. Apply update
   • Update plugin to 16.8 via Dashboard or SFTP (replace plugin files with patched version).
4. Verify and monitor
   • Confirm the plugin is functioning as expected.
   • Monitor logs and security scanner for anomalies.
5. Re-enable users/features (if you temporarily disabled them)
   • Re-enable registration or re-activate the plugin after confirming the patch.

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Incident response playbook — if you believe you were exploited

1. Contain
   • Immediately update the plugin to 16.8 (or deactivate it).
   • Revoke suspicious user sessions (Users -> All Users -> Sessions) or force password reset for all users.
   • Temporarily take the site into maintenance mode if needed.
2. Preserve evidence
   • Make a snapshot of the filesystem and database for later analysis.
   • Export server logs (web, PHP, system) and store them offline.
3. Assess scope
   • Determine which files were deleted and when (use logs and backups).
   • Identify whether other files were modified or malicious files added.
4. Eradicate
   • Restore deleted files from a known-good backup.
   • Replace any altered files with clean copies from backups or from plugin/theme vendor sources.
5. Recover
   • Bring site back online after full verification and patching.
   • Reset credentials: administrator passwords, FTP/SFTP/hosting control panel credentials, API keys that were used on the site.
6. Post-incident
   • Conduct a full malware scan and file integrity scan.
   • Communicate with stakeholders and customers as required by your policies (and regulatory requirements).
   • Harden the site to prevent recurrence (see the hardening checklist below).

If you do not have the in-house capacity to investigate, contact a professional incident response provider or your hosting provider for assistance.

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Hardening checklist (preventive measures to reduce blast radius)

1. Principle of least privilege for users
   • Only grant roles and capabilities that are necessary.
   • Remove unused accounts and limit registration.
2. Enforce strong authentication
   • Enforce strong passwords.
   • Enable Two-Factor Authentication (2FA) for privileged accounts.
3. Restrict plugin management
   • Only install trusted plugins, and limit installation capability to administrators.
   • Keep plugins/themes/core up to date.
4. File system permissions
   • Files: 644, Directories: 755 typically; wp-config.php 440/400 where possible.
   • Ensure the webserver user doesn’t have unnecessary write privileges to code directories.
5. Disable PHP execution in uploads
   • Prevent execution of PHP files in wp-content/uploads by placing .htaccess/Nginx rules to deny PHP execution.
6. Use file integrity monitoring
   • Alerts when core, plugin, or theme files change unexpectedly.
7. Regular backups
   • Keep frequent, automated backups with off-site retention. Test restoration regularly.
8. Limit exposure to plugin endpoints
   • Use an application-level firewall to restrict access to plugin endpoints, especially those that accept file or path input.
9. Logging and monitoring
   • Centralize logs, monitor for suspicious behavior, and configure alerting for suspicious events.
10. Harden hosting environment
    • Use separate SFTP accounts for each site where possible, use containerization, and ensure host-level isolation.

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Recovery checklist after restoring deleted files

• Confirm the installed plugin is updated to 16.8.
• Restore any deleted content from backup (media, themes, plugins).
• Replace compromised plugin/theme files with fresh copies from trusted sources.
• Run a full malware scan (both file system and database).
• Rotate credentials: WP admin passwords, SFTP/SSH, API keys, tokens.
• Check and reinstate proper file permissions/ownership.
• Re-enable monitoring and FIM.
• Document the incident: timeline, impact, steps taken, lessons learned.

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Can attackers pivot to remote code execution (RCE)?

Arbitrary deletion by itself is not RCE, but deletion can be used tactically by an attacker to:

• Remove logging and security plugins so subsequent attacks are easier.
• Remove innocuous files and replace them with malicious files if they already have upload capabilities.
• Combine with other vulnerabilities (e.g., insecure file upload, poorly configured file permissions) to achieve code execution.

Treat deletion as a severe event because it facilitates follow-up attacks and makes recovery harder.

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Communication advice for site owners / teams

• Be transparent internally: notify your ops and security team.
• If the incident affects customer data or service availability, follow your incident communication policy.
• If you rely on external vendors or managed hosts, inform them and provide logs to expedite remediation.
• Avoid posting technical details that could help attackers while the vulnerability is being exploited on live sites; instead, inform affected users that you are responding and will provide updates.

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How WP-Firewall can help you right now

At WP-Firewall we provide managed firewall and security services that can protect WordPress sites from attacks targeting known plugin vulnerabilities — even before you’re able to apply updates. Our platform includes a WAF with virtual patching capabilities, a malware scanner, and real-time protection designed specifically for WordPress environments.

Key protective features we recommend:

• Rule-based virtual patching to block exploit attempts targeting plugin endpoints.
• Rate-limiting for suspicious authenticated user traffic.
• File integrity monitoring and alerts for deleted or modified files.
• Automated malware scanning and remediation tools for quick containment.
• Detailed logging and incident alerts so you can act fast.

Below is a short paragraph describing our free plan and how it helps.

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Recommended mitigation checklist — condensed (actions you can do right now)

1. Check plugin version; if <= 16.7, update to 16.8 immediately.
2. If you cannot update, deactivate the plugin or rename the plugin folder.
3. Block plugin endpoint requests via WAF or host rules; rate-limit Subscriber POSTs.
4. Review server logs and user activity for signs of abuse.
5. Restore deleted files from backups if necessary.
6. Harden file permissions and disable PHP execution in uploads.
7. Force password resets for Subscriber accounts if suspicious activity detected.
8. Enable file integrity monitoring and continuous malware scanning.
9. Consider using a managed WAF / virtual patching service to stop exploit attempts while you patch.

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Final notes from a WordPress security practitioner

This vulnerability is a reminder that even widely-used, non-core plugins can contain logic errors that allow low-privileged users to cause significant damage. The best defense is a layered approach: keep software up to date, limit who can register or act on your site, use least-privilege file permissions, back up frequently, and run a WordPress-aware firewall that can virtual-patch dangerous endpoints.

If you find your site has been exploited, act quickly: contain, preserve evidence, restore from clean backups, and then harden the environment to prevent recurrence.

If you want help implementing virtual patches or immediate protection while you update, WP-Firewall’s managed firewall and security services were built to stop exploitation attempts like this in real time. Sign up for the Basic Free plan to get started immediately and protect your site while you work through remediation steps: https://my.wp-firewall.com/buy/wp-firewall-free-plan/

Stay safe and keep a clear recovery plan — quick action reduces damage and downtime.