Broken Access Control in Paytium (≤ 4.3.7) — What WordPress Site Owners Must Do Now

Quick technical summary

• Affected software: Paytium (Mollie payment forms & donations plugin) for WordPress
• Vulnerable versions: ≤ 4.3.7
• Fixed in: 4.4
• Vulnerability type: Broken Access Control (missing authorization check)
• CVE: CVE-2023-7290
• CVSS (reported baseline): ~4.3 (Low)
• Reported vector: an unauthorised or low-privileged request can trigger functionality that should be restricted (the function check_for_verified_profiles lacks proper authorization checks)
• Immediate action: update to 4.4 or later. If you cannot, apply virtual patch/WAF rules to block the vulnerable endpoint from untrusted actors.

Why this matters — impact & risk

Broken access control defects are common and often easy to exploit in practice. In this case the missing authorization check in the verified profiles function can allow a low-privileged or unauthenticated actor to change verification state that should be restricted.

Although the reported CVSS score is low, the practical risk is non-trivial:

• A manipulated “verified” flag undermines trust in donation or payment workflows.
• Depending on how the plugin uses verification, attackers may impersonate profiles, bypass moderation, or influence payment routing.
• Chaining with other weaknesses (CSRF, misconfigured payment APIs, or mail spoofing) can escalate impact.

Treat this as urgent: apply the vendor update promptly and use temporary mitigations if you cannot update immediately.

How the vulnerability works (technical explanation)

The vulnerable function (check_for_verified_profiles) performs profile verification without sufficient server-side authorization or nonce checks. Typical developer mistakes that lead to this include:

• Exposing an admin-ajax or REST endpoint without verifying capabilities (current_user_can()).
• Not verifying a nonce (with check_ajax_referer() or equivalent) to ensure requests came from legitimate UI flows.
• Relying on user-supplied data to determine privilege instead of performing server-side checks.
• Registering REST routes without a proper permission_callback.

When these checks are missing, low-privileged users (e.g., Subscribers) or unauthenticated requests can call the endpoint and mark profiles as verified or perform other sensitive operations.

Exploitation scenarios — what an attacker could do

We will not publish exploit code, but administrators should be aware of plausible attacks:

• A low-privilege authenticated user calls the vulnerable endpoint to mark profiles as verified, then abuses that status in donation or marketplace workflows.
• Automated scanners enumerate admin-ajax actions (e.g., admin-ajax.php?action=check_for_verified_profiles) and mass-exploit sites missing nonce/capability checks.
• Attackers use social engineering together with forged verification to request refunds, redirect funds, or solicit donations under false pretences.
• If profiles link to payment API tokens, manipulation could influence payment flows or webhook behavior.

Confirming whether you’re vulnerable

1. Identify plugin version
   • Dashboard > Plugins > locate “Paytium” and check version.
   • Or WP-CLI: wp plugin get paytium --field=version
2. If version ≤ 4.3.7, you are vulnerable until patched.
3. Search plugin code for exposed endpoints:
   • admin-ajax hooks: look for add_action('wp_ajax_check_for_verified_profiles', ...)
   • REST routes: register_rest_route('paytium/...', '/verified-profiles', [ 'permission_callback' => ... ])
4. Inspect access logs for calls to admin-ajax.php or the plugin’s REST route with suspicious parameters:

   GET /wp-admin/admin-ajax.php?action=check_for_verified_profiles
   POST /wp-admin/admin-ajax.php?action=check_for_verified_profiles&user_id=...

   Example log search:

   grep "admin-ajax.php" /var/log/nginx/access.log | grep "check_for_verified_profiles"

5. Review the relevant PHP functions for missing checks:
   • Expect to see check_ajax_referer(), check_admin_referer(), current_user_can() or a REST permission_callback.
   • If none are present, the endpoint is likely vulnerable.
6. If you use automated scanners, look for alerts mentioning CVE-2023-7290 or the check_for_verified_profiles action.

Step-by-step remediation (recommended)

1. Backup — take a full file and database backup before changes.
2. Update plugin — upgrade Paytium to 4.4 or later from the Plugins screen or with WP-CLI (wp plugin update paytium). Test donation/payment flows on staging before full deployment.
3. Temporary mitigation — if you cannot update immediately, apply a virtual patch/WAF rule (see examples below).
4. Verify the fix — confirm the endpoint now enforces capability and nonce checks and that unauthorised users cannot perform the action.
5. Audit logs and database — look for suspicious verified flags, payment settings changes, or new elevated accounts.
6. Rotate credentials — if compromise is suspected, rotate admin passwords and any payment API keys, and reset webhooks.
7. Monitor — continue monitoring access logs and alerts for follow-up activity.

Note: Vendor-provided fixes are the definitive resolution. Virtual patches are temporary mitigations only.

Manual patch snippet (responsible, minimal example)

If you must patch locally before updating the plugin, add proper authorization and nonce checks to the handler. Test on staging first.

// BEFORE: simplified vulnerable handler
function check_for_verified_profiles() {
    // existing logic that marks or checks profiles
    wp_send_json_success( array( 'message' => 'done' ) );
}
add_action( 'wp_ajax_check_for_verified_profiles', 'check_for_verified_profiles' );

// AFTER: add nonce and capability checks
function secure_protect_check_for_verified_profiles() {
    // 1) Verify AJAX nonce (adjust nonce name to match front-end)
    if ( ! isset( $_REQUEST['nonce'] ) || ! wp_verify_nonce( sanitize_text_field( wp_unslash( $_REQUEST['nonce'] ) ), 'paytium_verify_profiles' ) ) {
        wp_send_json_error( array( 'message' => 'Forbidden - invalid nonce' ), 403 );
    }

    // 2) Ensure user has appropriate capability
    if ( ! current_user_can( 'manage_options' ) ) {
        wp_send_json_error( array( 'message' => 'Forbidden - insufficient capability' ), 403 );
    }

    // 3) Continue existing logic safely. Sanitize inputs.
    $profile_id = isset( $_POST['profile_id'] ) ? intval( $_POST['profile_id'] ) : 0;
    if ( $profile_id <= 0 ) {
        wp_send_json_error( array( 'message' => 'Invalid profile id' ), 400 );
    }

    // perform verification logic here (sanitise and validate)
    wp_send_json_success( array( 'message' => 'Profile verified' ) );
}
remove_action( 'wp_ajax_check_for_verified_profiles', 'check_for_verified_profiles' );
add_action( 'wp_ajax_check_for_verified_profiles', 'secure_protect_check_for_verified_profiles' );
  

Use check_ajax_referer() or wp_verify_nonce() depending on your front-end. Choose a capability appropriate to your site's workflow — admin-level capabilities are conservative defaults. Sanitize all inputs.

Fast temporary mitigations (WAF / virtual patch examples)

If updating immediately is not possible, block or restrict access to the vulnerable action or route via your WAF, ModSecurity, server rules, or a site firewall plugin. The objective is to block unauthenticated or low-privileged calls to the endpoint.

1) Block admin-ajax action requests named check_for_verified_profiles

Rule intent: block requests to /wp-admin/admin-ajax.php where action=check_for_verified_profiles for unauthenticated or low-privileged users.

Example pseudo-rule:

Condition:
  REQUEST_URI contains "/wp-admin/admin-ajax.php"
  AND ARGS|action equals "check_for_verified_profiles"
  AND (REQUEST_METHOD is POST OR GET)
  AND (NOT cookie contains "wordpress_logged_in_" OR user role cookie indicates Subscriber)
Action: BLOCK (HTTP 403)
  

2) Block REST route calls for the plugin (if present)

Block requests that match the plugin REST namespace or verified-profiles path unless they originate from admin IPs or contain valid logged-in admin cookies and nonces.

3) Rate limit scanning attempts

Throttle or temporarily block IPs that make repeated calls to the vulnerable action within a short window.

4) ModSecurity example (adapt to environment)

# Block suspicious calls to Paytium's check_for_verified_profiles action
SecRule REQUEST_URI "@contains /wp-admin/admin-ajax.php" "phase:2,chain,deny,status:403,msg:'Blocked Paytium vulnerable action',id:1001001"
  SecRule ARGS:action "@streq check_for_verified_profiles" "t:none,chain"
  SecRule &REQUEST_HEADERS:Cookie "@gt 0" "t:none,chain"
  SecRule REQUEST_HEADERS:Cookie "!@rx wordpress_logged_in_[0-9a-fA-F_]+" "t:none"
  

5) Virtual rule guidelines

• Block any request to admin-ajax.php with action=check_for_verified_profiles unless the request comes from a whitelisted admin IP or contains a valid admin cookie and verified nonce.
• Alternatively, block the action entirely if your site does not require it.

6) Temporary plugin deactivation

If the plugin is not critical to immediate operations, consider deactivating it until you can apply the vendor patch. This is the most reliable short-term containment.

Remember: virtual patches are stop-gaps. Install the vendor patch as soon as possible.

Detection and forensic steps — what to look for if you suspect exploitation

1. Search access logs for admin-ajax or REST calls:

   grep "admin-ajax.php" access.log | grep "check_for_verified_profiles"
   grep "/wp-json" access.log | grep "paytium"

2. Review database for unexpected verification flags:

   SELECT * FROM wp_usermeta WHERE meta_key LIKE '%verified%';
   SELECT * FROM wp_postmeta WHERE meta_key LIKE '%verified%';

3. Check for new or elevated accounts:

   SELECT ID, user_login, user_email, user_registered FROM wp_users WHERE ID IN (SELECT user_id FROM wp_usermeta WHERE meta_key = 'wp_capabilities' AND meta_value LIKE '%administrator%');

4. Inspect plugin files and modification times:

   find wp-content/plugins/paytium -type f -mtime -30 -ls

   Compare files to a fresh vendor release if possible.

5. Scan for web shells and malicious files — look for suspicious base64, eval, or file write patterns.
6. Verify payment gateway settings — check receivers, webhook URLs, and API credentials; rotate keys if suspicious changes are found.
7. Audit WordPress logs and audit trails for actions performed during the timeframe of interest.
8. Check scheduled tasks — examine wp-cron entries for unexpected jobs.
9. Preserve evidence — export logs and database snapshots for forensic analysis before making irreversible changes.

Hardening checks to prevent similar issues

• Principle of least privilege — ensure sensitive functions require appropriate capabilities; never trust client-supplied privilege indicators.
• Use nonces and permission callbacks — all state-changing AJAX/REST actions must verify nonces or have robust permission callbacks.
• Server-side validation — sanitize and validate all inputs and ID ranges.
• Reduce attack surface — disable features or endpoints you do not use.
• Keep software updated — apply plugin, theme, and core updates on a regular cadence and test on staging.
• Logging and monitoring — capture admin-ajax and REST calls, retain logs sufficiently long for investigations.
• Code review and testing — review third-party code for auth checks and run targeted tests for AJAX/REST endpoints.
• WAF and rate limiting — deploy rules for common plugin endpoints and throttle suspicious behavior.

Incident response playbook (condensed)

1. Isolate — show a maintenance page, restrict public access, and block suspicious IPs.
2. Snapshot — take immediate full backups (files + DB) for analysis.
3. Contain — apply virtual patch/WAF rule or deactivate the vulnerable plugin.
4. Eradicate — remove malicious files, reinstall clean plugin files from the vendor, and remove unauthorized accounts.
5. Recover — rotate credentials and API keys, verify systems are clean, then restore normal operations and apply vendor patch (update to 4.4+).
6. Post-incident — perform root-cause analysis, document lessons learned, and update controls.

If payments are critical, inform your payment provider so they can assist with credential rotation or suspicious transaction reviews.

Practical checklist — what to do now

• Verify the plugin version. If ≤ 4.3.7, update to 4.4+ immediately.
• Backup site files and database before changes.
• If you cannot update immediately:
  • Deploy a WAF rule to block admin-ajax.php?action=check_for_verified_profiles
  • Block the plugin REST route as necessary
  • Throttle repeated requests and block suspicious IPs
• Search logs for exploitation indicators: admin-ajax.php?action=check_for_verified_profiles, suspicious REST calls, and abnormal traffic.
• Rotate credentials if you detect suspicious activity: WP admin passwords, payment API credentials, and webhooks.
• After updating, validate donation/payment flows on staging before re-enabling normal traffic.
• Long-term: enforce plugin security reviews and retain a process for rapid virtual patching when new vulnerabilities are disclosed.

Final notes — Hong Kong security perspective

Broken access control often appears as a small oversight in code but can have outsized consequences in payment and donation environments. For organisations operating in Hong Kong and the wider APAC region where trust and donor confidence are paramount, even subtle manipulation of verification flags can damage reputation and have financial implications.

Practical advice: prioritise the vendor update to 4.4, apply temporary mitigations if you cannot update immediately, and follow the detection and forensic steps above if you suspect any misuse. Keep a calm, methodical approach: contain, collect evidence, patch, and then restore services only after verification.

Signed,
Hong Kong Security Expert

Appendix: Useful commands & queries

• Check plugin version with WP-CLI:

  wp plugin get paytium --field=version

• Search webserver logs:

  grep "admin-ajax.php" /var/log/nginx/access.log | grep "check_for_verified_profiles"

• Find recently modified files in the plugin:

  find wp-content/plugins/paytium -type f -mtime -30 -ls

• Search for suspected meta keys:

  SELECT * FROM wp_usermeta WHERE meta_key LIKE '%verified%';

• Check for new admin accounts:

  SELECT ID, user_login, user_email FROM wp_users WHERE ID IN (SELECT user_id FROM wp_usermeta WHERE meta_key = 'wp_capabilities' AND meta_value LIKE '%administrator%');

References

• Plugin changelog — consult the plugin developer’s official changelog for details on v4.4 fixes.
• Preserve and test updates on staging environments before rolling out to production.
• Adapt the pseudo-rules above to your firewall console or ModSecurity implementation as needed.