Nombre del complemento	Thim Core
Type of Vulnerability	Control de acceso roto
CVE Number	CVE-2025-53346
Urgencia	Bajo
CVE Publish Date	2025-08-14
Source URL	CVE-2025-53346

Thim Core Plugin (≤ 2.3.3) — Broken Access Control (CVE-2025-53346): What WordPress Site Owners and Developers Need to Know

Autor: WP-Firewall Security Team
Fecha: 2025-08-14

Executive summary

A broken access control vulnerability has been disclosed in the Thim Core WordPress plugin (versions ≤ 2.3.3) and assigned CVE-2025-53346. The issue allows an authenticated user with Subscriber-level privileges to trigger actions that should be restricted to higher-privileged roles. The vulnerability has been scored CVSS 4.3 (Low), and at the time of publication there is no official vendor-supplied fix.

While the severity rating is low, the weakness is real and should be treated carefully — especially on multi-author or public-registration sites. This article explains the risk, how to detect whether you’re affected, short-term and long-term mitigations, developer-level fixes, incident response steps if you suspect compromise, and how managed virtual patching and WAF protections can help keep you safe until an official update is available.

This post is written by the WP-Firewall security team with pragmatic, hands-on guidance for site owners, operators, and developers.

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What is the vulnerability?

Broken access control refers to situations where a plugin or theme fails to correctly check whether the currently authenticated user has the necessary privileges to perform a sensitive action. In this case, an endpoint or function within Thim Core is callable by a user with Subscriber-level privileges, when the intended behavior requires a higher privilege. The result is that a low-privileged account can perform operations that should be restricted — for example, triggering data changes, initiating background tasks, or modifying content/settings.

Key facts:

• Affected software: Thim Core plugin (WordPress)
• Vulnerable versions: ≤ 2.3.3
• CVE: CVE-2025-53346
• CVSS: 4.3 (Low)
• Required attacker privilege: Subscriber (authenticated)
• Official fix: Not available (as of publication)
• Reported by: independent researcher
• General class: Broken Access Control / OWASP A1

Important: Broken access control vulnerabilities vary by context. Some code paths may be benign while others may enable more impactful changes in specific site configurations. The attacker requirement of a Subscriber account reduces the scope compared with unauthenticated vulnerabilities, but many WordPress sites allow registrations or have subscribers, so risk remains.

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Who should be concerned?

• Sites using the Thim Core plugin at versions ≤ 2.3.3.
• Sites that allow user registration or where accounts may be upgraded or created by third parties.
• Multi-author sites where contributors/clients have Subscriber-level accounts.
• Hosts and managed WordPress providers responsible for many sites using the plugin.

If you run the plugin and any untrusted person can create or hold a Subscriber account on your site, treat this as actionable.

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How to check if you are vulnerable

1. Site admin dashboard:
   • Go to the Plugins page (WordPress admin → Plugins).
   • Look for the plugin named “Thim Core” and note its version number.
   • If the version is 2.3.3 or earlier, you are within the vulnerable set.
2. File system check (SSH or file manager):
   • Search plugin directory: /wp-content/plugins/thim-core/
   • If the plugin folder exists and contains plugin headers that indicate version ≤ 2.3.3, assume you are affected.
3. Automated scans:
   • Run your site scanner or WAF log search for requests invoking plugin endpoints. Look for POST/GET requests containing plugin-specific parameters or file paths under /wp-content/plugins/thim-core/.
4. Check user roles:
   • If you allow registration or have Subscriber users, evaluate whether those accounts could carry out privileged actions in practice.

If you are unsure, take conservative steps (see mitigation below) while you confirm.

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Immediate mitigation steps (site owner / operations)

If you run an affected site, prioritize defense-in-depth while waiting for an official plugin update:

1. Update or remove
   • If a fixed release becomes available, update immediately.
   • If no fix exists and you do not need the plugin functionality, deactivate and remove the plugin until a safe version is released.
2. Restrict user registration and review Subscriber accounts
   • If your site allows open registration, temporarily disable registration (Settings → General → Membership).
   • Audit existing Subscriber accounts, look for unfamiliar accounts, and remove any that are unrecognized.
   • Force a password reset for suspicious or critical accounts.
3. Harden the Subscriber role
   • Use a role-management plugin or functions.php filters to temporarily remove capabilities from Subscriber that could be leveraged (e.g., if Subscribers were granted custom capabilities).
   • Deny elevated privileges beyond the default Subscriber set.
4. WAF / virtual patching
   • If you operate a web application firewall (WAF) or use a managed firewall service, enable rules to block known exploit patterns for Thim Core endpoints. WP-Firewall can deploy virtual patch rules that block the vulnerable request patterns at the edge until the plugin is patched.
5. Block plugin-specific endpoints at webserver level (temporary)
   • If the vulnerable code resides in a discrete file or endpoint, consider blocking direct public access to it via .htaccess / nginx rules while still allowing admin users to operate. Example (Apache .htaccess):

   # Block direct access to a plugin file (adjust path and filename)
   <Files "vulnerable-endpoint.php">
       Require ip 127.0.0.1
       Require all denied
   </Files>
       

   Only use webserver block rules if you can confirm the targeted file and avoid breaking legitimate site functionality. Prefer WAF virtual patches where available.

6. Monitor logs
   • Increase monitoring for suspicious POST requests, changes to plugin files, creation of posts, or unexpected admin actions. Check access logs and WordPress activity logs.
7. Respaldo
   • Ensure you have a recent off-site backup. If you need to recover from compromise, having a clean backup is essential.

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Developer guidance (how to fix the plugin)

If you maintain the affected plugin code or can influence the vendor, the problem typically comes from missing capability checks, missing nonce verification, or insecure REST / AJAX endpoints. Fixes should be made in the plugin and released as an official update. Below are practical developer steps.

1. Add explicit permission checks

   For admin or sensitive actions, always validate the current user’s capability with current_user_can().
   Do not assume authentication implies authorization.

   if ( ! is_user_logged_in() || ! current_user_can( 'manage_options' ) ) {
       wp_send_json_error( 'Permission denied', 403 );
       exit;
   }
       

2. Validate nonces for AJAX and form actions

   Use wp_nonce_field() and check_ajax_referer() for form-based or AJAX actions that change state.

   // On form render:
   wp_nonce_field( 'thim_core_sensitive_action', 'thim_core_nonce' );
   
   // On process:
   if ( ! isset( $_POST['thim_core_nonce'] ) || ! wp_verify_nonce( $_POST['thim_core_nonce'], 'thim_core_sensitive_action' ) ) {
       wp_send_json_error( 'Invalid request', 400 );
       exit;
   }
       

3. Secure REST API endpoints

   When registering REST routes, supply a permission_callback that checks capabilities, not just authentication.

   register_rest_route( 'thim-core/v1', '/sensitive', array(
       'methods'  => 'POST',
       'callback' => 'thim_core_sensitive_handler',
       'permission_callback' => function() {
           return current_user_can( 'manage_options' );
       }
   ) );
       

4. Principle of least privilege

   Design plugin functionality so that only the smallest necessary capability is required to perform an action. Avoid granting Subscribers any custom elevated capabilities.

5. Sanitize inputs and output

   Use sanitize_text_field(), intval(), esc_html() etc., and use prepared statements for database writes.

6. Unit and integration tests

   Add tests that demonstrate a Subscriber account cannot perform sensitive actions. Automate regression tests to catch similar authorization errors in the future.

7. Release process

   Publish a patch, bump plugin version, and clearly document the security fix in changelog and advisory. Users should be informed via plugin update notice and email/newsletter where relevant.

If you are not the plugin author, encourage the vendor to follow these steps and request a secure release.

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Suggested WAF rules (conceptual)

If you operate a WAF, virtual patching is the fastest way to stop exploitation on production sites while code fixes are delivered. Do not block legitimate admin traffic; craft precise rules.

• Block requests to specific plugin file paths with identifying POST parameters.
• Deny POST requests from non-admin users for routes that should be admin-only.
• Detect and block requests with abnormal parameter values or user-agent patterns related to exploitation scans.

Example pseudo-rule (conceptual):

IF request URI contains “/wp-content/plugins/thim-core/” AND request method == POST AND (referer is external OR user role cookie indicates non-admin) → block.

Note: Actual rule syntax differs between WAF products; test carefully to avoid false positives.

WP-Firewall customers receive tuned virtual patches targeted at vulnerability indicators without modifying site code.

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How to tell if you were exploited

Because this vulnerability requires an authenticated Subscriber, exploitation signs might be subtle. Look for:

• New or modified posts/pages, especially by Subscriber accounts.
• Unexpected scheduled tasks (wp-cron) or background jobs.
• New admin users created or changes to user roles/capabilities.
• Files created in /wp-content/uploads/ or plugin/theme directories.
• Unknown outgoing connections from site (malware exfiltration).
• Suspicious entries in access logs: repeated requests to plugin endpoints from user accounts or IPs.

Use forensic tools:

• WordPress activity logs (if enabled)
• Server access and error logs
• File integrity monitoring (compare current files to a clean backup)
• Malware scanners

If you find indicators of compromise, follow the incident response steps below.

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If your site is compromised — an incident response checklist

1. Isolate
   • Put the site into maintenance mode or block traffic from suspicious IPs.
   • If you have a staging environment, spin it down to prevent further spread.
2. Preserve evidence
   • Make copies of logs and affected files for later analysis before making changes.
3. Respaldo
   • Take a full backup of the current site (even if infected) to preserve data for analysis.
4. Reset credentials
   • Reset admin and all user passwords, especially those with higher privileges.
   • Rotate API keys and database credentials if they may have been exposed.
5. Clean or restore
   • Restore from a clean backup taken before compromise, OR
   • Use a reputable malware removal process to clean infected files. If you lack in-house expertise, consider engaging professional incident responders.
6. Patching and hardening
   • Remove or update the vulnerable plugin.
   • Apply principle of least privilege to user accounts.
   • Harden filesystem permissions and wp-config.php protections.
   • Install and enable hardening controls: WAF, file integrity monitoring, strong authentication.
7. Post-incident monitoring
   • Increase logging and monitoring for at least 30 days.
   • Conduct an audit of plugins/themes and user accounts.
8. Inform stakeholders
   • Notify site owners, affected users, and legal/compliance teams if sensitive user data was exposed.

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Recommendations for site administrators and managers

• Treat all published vulnerabilities seriously, even those rated low. Attackers can combine low-severity flaws with other vectors.
• Maintain an inventory of plugins and their versions. Automated vulnerability scanners are helpful.
• Apply updates promptly, but plan updates with backups and staging to avoid breaking production.
• Use multi-layer defenses: network WAF, site-level WAF, strong passwords, two-factor authentication for admins, and least-privilege principles.
• Limit user registration and restrict default Subscriber capabilities on sites where registration is not needed.
• Monitor logs and use alerting to detect suspicious behavior early.

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Recommendations for developers and plugin vendors

• Implement authorization and nonce checks for every request that changes state.
• Use the REST API’s permission_callback on custom endpoints.
• Provide a public Security / Vulnerability Disclosure Program (VDP) and respond quickly to reported issues.
• Release security patches promptly and provide guidance to site owners about mitigations while a patch is prepared.
• Include automated tests that assert unauthorized roles cannot call sensitive functions.

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Example quick fixes you can apply now (for plugin developers)

Below are non-exhaustive examples to illustrate how to harden endpoints. These are illustrative and should be integrated into proper plugin architecture and tested.

1. Protect AJAX handlers:

   add_action( 'wp_ajax_thim_core_sensitive', 'thim_core_sensitive_handler' );
   function thim_core_sensitive_handler() {
       // Ensure user has correct capability
       if ( ! current_user_can( 'manage_options' ) ) {
           wp_send_json_error( array( 'message' => 'Unauthorized' ), 403 );
       }
   
       // Verify nonce
       check_ajax_referer( 'thim_core_sensitive_action', 'nonce' );
   
       // Proceed with action...
   }
       

2. Protect REST endpoints (permission_callback):

   register_rest_route( 'thim-core/v1', '/do-something', array(
       'methods'  => 'POST',
       'callback' => 'thim_core_do_something',
       'permission_callback' => function( $request ) {
           return current_user_can( 'manage_options' );
       }
   ) );
       

3. Avoid relying on user-submitted role values or hidden form fields to grant privilege. Always use current_user_can().

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Why virtual patching matters (and how it helps)

Virtual patching is an operational mitigation applied at the WAF or edge that blocks exploit attempts before they reach your WordPress instance. It is especially useful when:

• There is no official vendor patch yet.
• You cannot safely or immediately update the plugin (customization, compatibility concerns).
• You need time to test an update in staging before rolling it to production.

Virtual patches do not modify plugin code; they stop attack patterns, protecting large sites at scale and buying time to apply a proper fix. If you do not have a WAF or managed firewall enabled, consider deploying one while you wait for a plugin update.

WP-Firewall provides managed virtual patch rules tailored to vulnerabilities like this one and can deploy protection to affected customer sites quickly.

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Frequently asked questions (FAQ)

Q: My site does not allow user registration — am I safe?
A: If your WordPress installation does not allow untrusted accounts and all existing Subscriber accounts are trusted, the immediate risk is lower. However, attackers may still create accounts via other vulnerabilities or exploit social engineering to gain accounts, so keep monitoring and patch when available.

Q: Can I just hide the plugin directory to prevent exploitation?
A: Hiding the plugin directory is not a reliable security control. Attackers often find endpoints via requests and discovery. Use permission checks in code and WAF controls for reliable protection.

Q: Will removing the plugin break my site?
A: Possibly. If theme functionality depends on Thim Core, removing it may break features or layouts. If you must remove it temporarily, test on staging and notify stakeholders about potential visual or functionality impacts.

Q: How long should I keep virtual patches?
A: Virtual patches should be in place until you have applied and verified the vendor-supplied code update and performed regression testing. After patching, monitor and remove virtual rules when safe.

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Timeline (publicly known)

• 13 Nov 2024 — Initial researcher discovery and reporting to plugin vendor.
• 14 Aug 2025 — Public disclosure and advisory published; CVE assigned (CVE-2025-53346). No official fix available at time of publication.

If you are a plugin vendor and received a report, follow responsible disclosure guidelines and publish a fix and clear communications to users.

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Practical checklist — what to do right now (quick win list)

• Identify if Thim Core is installed and version ≤ 2.3.3.
• If possible, update to a fixed version when released.
• Disable user registration if not needed.
• Audit Subscriber accounts and remove suspicious ones.
• Enable or request virtual patching from your WAF provider.
• Temporarily restrict or block the plugin endpoint if you can identify it safely.
• Increase log monitoring for unusual activity.
• Create a clean backup before making changes.

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Final thoughts from the WP-Firewall security team

Broken access control bugs are preventable with good secure coding practices: always check capabilities and nonces, design endpoints with clear permission models, and avoid trusting client-supplied role or capability indicators. For site owners, the fastest way to reduce exposure is to limit untrusted user accounts, enable WAF protections (virtual patches), and keep a good backup and recovery plan in place.

If you manage multiple WordPress sites or host customers who might be affected, treat this as a maintenance priority: apply virtual protections immediately, schedule plugin updates after testing, and audit accounts. We stand ready to help customers deploy virtual patches and monitoring to keep sites secure while vendors release official fixes.

If you need help interpreting logs, applying mitigations, or getting virtual patch coverage for your WordPress estate, WP-Firewall’s team is available to help — start with the free managed protection plan above to get immediate coverage.

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References & further reading

• CVE-2025-53346 (public advisory)
• WordPress developer handbook: Roles and Capabilities, Nonces, REST API permissions
• OWASP: Broken Access Control guidance