Plugin Name	Modula Image Gallery
Type of Vulnerability	Access Control Vulnerability
CVE Number	CVE-2025-13891
Urgency	Low
CVE Publish Date	2026-01-30
Source URL	CVE-2025-13891

Broken Access Control in Modula Image Gallery (<= 2.13.3) — What site owners and developers must do now

Published: 30 January 2026
CVE: CVE-2025-13891
Affected: Modula Image Gallery plugin for WordPress (versions <= 2.13.3)
Fixed in: 2.13.4
Severity (Patchstack-style): Low priority / CVSS 6.5 (A1: Broken Access Control)

Recently a responsible disclosure reported a broken access control problem in the Modula Image Gallery WordPress plugin that allowed an authenticated user with Author-level privileges to trigger an endpoint that lists directories arbitrarily. The issue was fixed in version 2.13.4. As a team that builds and operates a managed WordPress Web Application Firewall (WAF) and security services, we want to provide site owners, administrators, and plugin developers with a clear, practical playbook: what happened, how to evaluate exposure, what to do immediately, and how to harden WordPress and plugin code to prevent similar problems in the future.

This article is written from the perspective of an experienced WordPress security provider and product team. Our aim is to be practical — with steps you can take today, detection patterns to watch for, mitigations that reduce risk immediately, and developer guidance for robust authorization checks.

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What happened — short technical summary

• The vulnerability is a broken access control issue present in Modula Image Gallery plugin versions up to and including 2.13.3.
• An endpoint within the plugin allowed an authenticated user with the Author role to request a directory listing for an arbitrary server path (or plugin-managed path), due to missing or insufficient authorization checks.
• The issue is classified as “Broken Access Control” and was assigned CVE-2025-13891. The disclosure credits a security researcher.
• The vendor released version 2.13.4 to address the problem. The fix includes proper capability checks and/or nonce validation and sanitization that prevents arbitrary directory enumeration by low-privileged users.

Why this matters: directory listing leaks filenames and structure. That can disclose sensitive data (backup files, configuration files, plugin files, media filenames) that enable follow-up attacks — targeted file read attempts, information leakage leading to privilege escalation, or identification of further vulnerable components.

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Who is affected and how dangerous is it?

• A site running a vulnerable Modula Image Gallery version (<= 2.13.3) is affected.
• The vulnerability requires at least the Author role to trigger. That lowers the scope compared to a fully unauthenticated vulnerability but remains seriously relevant because many sites allow user registrations or have multiple content creators.
• Impact classification:
  • Confidentiality: High (C:H) — directory listing can expose sensitive filenames and paths.
  • Integrity: Low/None — this issue doesn’t directly write files or modify content.
  • Availability: Low/None — doesn’t by itself crash or DoS the site.
• Exploitability: Moderate — any Author account (or compromised Author account) on a target can exploit this. If your site permits Author signups or has weak admin processes, this increases risk.
• Real-world threat: An attacker could enumerate directories, identify private uploads, find backup files or credentials accidentally stored in the webroot, and then exploit other vulnerabilities to escalate.

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Immediate steps for site owners (incident avoidance)

If you run WordPress and use Modula Image Gallery, follow these immediate steps.

1. Check plugin version now
   Login to WordPress admin → Plugins and confirm Modula version. If it’s <= 2.13.3, consider the site vulnerable until patched.
2. Update the plugin
   Upgrade Modula Image Gallery to version 2.13.4 or later immediately. This is the single most effective fix.
3. Temporarily restrict plugin access
   If you cannot update immediately, temporarily deactivate the plugin until you can apply the patch.
   If deactivation is impossible because of site functionality needs, restrict access to the plugin’s endpoints via server configuration or WAF rules (examples below).
4. Audit user roles and registrations
   Audit all Author-level accounts. Disable or remove accounts you don’t recognize.
   If your site allows public registration, consider switching to Subscriber-only registration, requiring manual approvals, or enabling email verification and stricter moderation.
5. Search for suspicious files
   Look for unusual files (backup files, .sql dumps, files with trending timestamps) in your uploads directory and plugin folders.
   Check for .bak, .sql, .old, .zip, .tar, .env, and other artifacts that shouldn’t be web-accessible.
6. Rotate credentials if necessary
   If you find evidence of a compromise or signs of reconnaissance, rotate any credentials that may be exposed (API keys, database credentials, admin passwords).
7. Enable logging and monitoring
   Ensure access logging is enabled. Keep logs for incident response. Increase log retention temporarily to aid analysis.
8. Scan for malware
   Run a full site malware scan. The directory listing itself doesn’t install malware, but it can be used to prepare targeted attacks.

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How to detect attempted exploitation

Look for the following indicators in your access logs and application logs.

• Requests to plugin-specific endpoints (check the plugin’s code to identify endpoint paths). Typical patterns:
  • GET or POST requests with parameters like dir=, path=, folder=, location=, listing=, or similar.
  • Requests from Author accounts (or sessions where cookies indicate authenticated users).
• Repeated requests that iterate through various path parameters: enumeration scanning patterns often increment paths or try common folder names (e.g., wp-content/uploads/, wp-config.php lookups).
• Responses that return directory listings or arrays of filenames and sizes, particularly with HTTP 200 OK responses when the parameter is changed.
• Unusual user activity from accounts that normally do not access plugin endpoints (Authors requesting administrative-like endpoints).
• Example log snippet you might see:
  • 2026-01-30T09:12:03 GET /wp-admin/admin-ajax.php?action=modula_list&path=../../.. 200 — User: [email protected]
  • 2026-01-30T09:12:05 GET /wp-admin/admin-ajax.php?action=modula_list&path=/etc 200 — User: [email protected]

Set up alerts for these patterns in your logging system (Cloud logs, SIEM, or your WAF product).

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Tactical WAF & server-side mitigations (fast protective measures)

If you cannot patch and must protect production quickly, apply these mitigations immediately. These are the types of virtual patches a WAF can apply.

1. Block access to the vulnerable endpoint for non-admins
   Implement a rule that blocks requests to the plugin’s directory-listing endpoint unless the request originates from an admin-level user session (server-side cookie heuristics) or specific internal IPs.
2. Disallow directory traversal patterns
   WAF rule: block any request containing path traversal tokens like ../, ..\, URL-encoded ..%2f etc. Many directory-listing endpoints become powerful when combined with traversal.
3. Sanitize/validate path parameter
   WAF rule: enforce that the path parameter matches a safe whitelist pattern (e.g., ^/wp-content/uploads/[\w\-/]+$) — block anything outside expected upload/media directories.
4. Rate-limit and fingerprint scanning patterns
   Add rate-limits for requests by the same user or IP to the plugin endpoint. Enumeration tends to be repetitive.
5. Block requests that return directory-like JSON or HTML
   If you know what the directory-listing response looks like, you can tune a WAF signature to block requests that both match the endpoint and generate a response containing file-list patterns.
6. Disable public write/read to sensitive plugin folders using server config
   Apache: deny access to directories with sensitive files via .htaccess.
   Nginx: use location blocks to return 403 for suspicious paths.

Example Nginx snippet to block traversal-based requests:

# Block directory traversal attempts at entry points
if ($request_uri ~* "\.\./|\.\.\\|%2e%2e") {
    return 403;
}

Example Apache .htaccess snippet to deny listing plugin directories:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{QUERY_STRING} (\.\./|%2e%2e) [NC]
RewriteRule .* - [F]
</IfModule>

# Prevent direct access to sensitive files
<FilesMatch "\.(sql|env|bak|tar|zip)$">
    Order allow,deny
    Deny from all
</FilesMatch>

A managed WAF can deploy these protections immediately as virtual patches until the plugin is updated.

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Developer guidance — how this should have been coded

For plugin authors, this is a classic case where authorization and input validation were not implemented correctly. The following is a checklist and code patterns you should adopt in your WordPress plugin endpoints (AJAX, REST, admin pages):

1. Capability checks
   Use the appropriate capability check for the operation. If an action is administrative (e.g., reading server directory listings), require manage_options or a capability at least as strict as edit_plugins or upload_files depending on the context.
   Example:

   if ( ! current_user_can( 'manage_options' ) ) {
       wp_send_json_error( 'Unauthorized', 403 );
   }
   

2. Nonce protection
   Add nonces for any AJAX or REST action and validate server-side with check_ajax_referer() or wp_verify_nonce().

   check_ajax_referer( 'modula_admin_action', 'security' );
   

   Do not rely solely on nonce for privilege differentiation — combine with capability checks.

3. Parameter sanitization and whitelisting
   Never accept arbitrary paths from clients. Use a whitelist of allowed base directories and sanitize the rest.
   Example:

   $allowed_bases = array(
       wp_get_upload_dir()['basedir'],
       WP_CONTENT_DIR . '/plugins/modula'
   );
   
   $path = wp_normalize_path( sanitize_text_field( $_POST['path'] ?? '' ) );
   $real_path = realpath( $path );
   
   $allowed = false;
   foreach ( $allowed_bases as $base ) {
       if ( strpos( $real_path, realpath( $base ) ) === 0 ) {
           $allowed = true;
           break;
       }
   }
   
   if ( ! $allowed ) {
       wp_send_json_error( 'Invalid path', 403 );
   }
   

4. Avoid returning detailed system-level information
   When you return file lists, do not include full filesystem paths, server paths, or other metadata that provides internal structure. Keep responses minimal and contextual.
5. Least privilege principle
   Only expose features to users who genuinely need them. If an operation is intended for admins, do not let Authors or Editors trigger it.
6. Logging and audit hooks
   Log sensitive operations (who did what, what path was requested) and consider adding admin notifications for unusual access.
7. Unit & integration tests
   Add tests asserting that low-privileged users cannot access admin-level endpoints. Tests should cover capability checks, nonce checks, and parameter traversal attempts.

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Incident response checklist (if you find evidence of use)

If you detect evidence of exploitation — enumeration logs, suspicious file reads, or unauthorized file access — follow this checklist.

1. Isolate
   If possible, disable the vulnerable plugin or block the endpoint at WAF/server level.
2. Preserve logs
   Archive web server logs, application logs, and WAF logs for analysis.
3. Collect indicators of compromise (IoCs)
   Collect IP addresses, user accounts used, request URIs, parameters, timestamps.
4. Scan for further compromise
   Use malware scanners and manual inspection. Check scheduled tasks, modified files, and unknown administrative users.
5. Rotate secrets
   Rotate API keys, database credentials, and other secrets that may have been exposed.
6. Restore from clean backups if necessary
   If you find injected files or persistence, consider restoring from a clean backup that predates the compromise.
7. Notify stakeholders
   Inform site owners, administrators, and any parties that might be affected if sensitive data was exposed.
8. Apply the patch & harden
   Upgrade the plugin to 2.13.4 or later and apply the developer guidance above. Deploy WAF rules to prevent recurrence.

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Example WAF signatures and rule logic (for security ops)

Below are conceptual rule signatures—you’ll need to adapt them to your WAF or IDS product.

1. Block simple traversal attempts:
   • Condition: Request URI or any parameter contains ../ or URL-encoded forms (%2e%2e, %2f adjacent to ..).
   • Action: Block + log.
2. Block requests to Modula directory-listing endpoints from non-admins:
   • Condition: POST/GET to admin-ajax.php or REST route modula/* with action param modula_list and user role cookie not admin.
   • Action: Block + return 403.
3. Whitelist expected path patterns:
   • Condition: Parameter path does not match regex ^(/wp-content/uploads/|/wp-content/plugins/modula/)[\w\-/]*$
   • Action: Block + trigger alert.
4. Rate-limit enumeration:
   • Condition: More than N requests to endpoint in T seconds by same user/IP.
   • Action: Throttle or temporary ban.

Note: rule implementation requires tuning to avoid false positives. Test in monitoring mode first.

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Hardening best practices beyond the immediate fix

• Enforce the principle of least privilege for site users. Review roles periodically.
• Disable user registration if not needed. If needed, use moderation and email verification.
• Keep WordPress core, themes, and plugins updated with an integrated patch management process.
• Implement file system protections:
  • Disable PHP execution in upload directories where not strictly required:
    • Place an .htaccess file in /wp-content/uploads/ to deny execution of .php files.
  • Restrict access to backup and development artifacts.
• Maintain a separation of environments: do development outside of production and avoid committing secrets to webroot.
• Use multi-factor authentication (MFA) for all admin accounts and critical editor accounts.
• Monitor logs and set alerts for unusual activity.

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For plugin authors: recommended patch checklist

If you maintain a plugin, run through this checklist whenever you add any endpoint that interacts with the filesystem or with data outside of normal user content.

• [ ] Are capability checks present and appropriate?
• [ ] Are nonces used and validated for AJAX/REST actions?
• [ ] Are all inputs sanitized and validated against whitelists?
• [ ] Is path input canonicalized and restricted using realpath checks?
• [ ] Are responses sanitized to prevent leaking server paths and metadata?
• [ ] Are unit/integration tests covering privilege boundaries?
• [ ] Do you have logging for sensitive operations?
• [ ] Do you avoid running file-system operations with elevated privileges?

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Why a managed WAF and layered protection matters

This vulnerability illustrates a common pattern: even when plugin authors fix a bug, many sites remain vulnerable until the patch is deployed. Vulnerabilities that allow low-privileged user actions to glean internal structure are particularly nasty: they can be silently abused and set the stage for larger attacks.

A managed WAF provides immediate, protective virtual patching by applying rules to block exploit attempts before you can update the plugin. Combined with a malware scanner, user role controls, and proactive monitoring, a layered approach significantly reduces the window of exposure between vulnerability disclosure and patch application.

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Final notes & recommended timeline

1. Right now: verify Modula version and update to 2.13.4 if you haven’t already.
2. Within 24 hours: audit Author accounts; enable tighter registration policies; enable logging and scanning.
3. Within 72 hours: deploy WAF rules or virtual patching if you cannot update immediately.
4. Within 7 days: perform a site-wide scan, inventory third-party plugins, and apply a hardening checklist.
5. Long term: implement continuous monitoring, automated plugin updates (carefully), and regular security reviews.

If you’re running a busy site with multiple authors or public registrations, treat this issue as a priority even though the vulnerability requires Author privileges. Attackers often use compromised or malicious Author accounts for reconnaissance. Closing that reconnaissance vector is essential to reduce risk.

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If you’d like guidance tailored to your environment — custom WAF rules, log review assistance, or help with remediation and monitoring — we can assist with an incident review and mitigation plan tuned for your WordPress site.