Summary

A critical Broken Access Control vulnerability (CVE-2025-11890, CVSS 7.5) affects the
“Crypto Payment Gateway with Payeer for WooCommerce” plugin (versions ≤ 1.0.3). An unauthenticated attacker can mark orders as paid without a valid payment notification from the payment processor. This allows free delivery of digital goods, unlocking of accounts/downloads, and significant reconciliation and financial disruption for merchants.

This advisory, written from the perspective of a Hong Kong security expert, explains the technical root cause, likely exploitation scenarios, detection indicators, immediate mitigations (including generic WAF/virtual-patch guidance), an incident response checklist, and secure development guidance for plugin authors.

If your site uses the affected plugin, act now.

Who should read this

• WooCommerce store owners using any Payeer/crypto payment integrations.
• WordPress administrators and hosting providers managing WooCommerce stores.
• Site security teams responsible for incident response and fraud detection.
• Developers maintaining payment gateway plugins or implementing webhook handlers.

Vulnerability at a glance

• Vulnerability type: Broken Access Control — unauthenticated payment bypass
• Affected software: Crypto Payment Gateway with Payeer for WooCommerce plugin
• Vulnerable versions: ≤ 1.0.3
• CVE: CVE-2025-11890
• Severity: High — CVSS 7.5
• Required privileges to exploit: Unauthenticated (no account required)
• Official fix: Not available at time of disclosure (N/A)
• Disclosure date: 4 November 2025

What went wrong (technical overview)

Payment gateway plugins expose endpoints (webhooks/IPNs/return handlers) that payment processors call to notify a shop about completed payments. Secure webhook implementations must:

• Verify authenticity (signature, HMAC, token, shared secret).
• Confirm payment details (order ID exists, amount and currency match).
• Validate source (IP allowlist or cryptographic signature).
• Ensure idempotency (prevent replay or duplicate marking).

In this case the plugin’s notification handler lacks adequate authorization and signature verification. A crafted HTTP request to the notification URL can be accepted as a valid payment notification even though it did not originate from Payeer. The plugin then marks the associated WooCommerce order as “paid” or “completed” without a real payment.

The attack requires no authentication, is easy to automate and scale, and can be used to obtain digital goods, create refunds, and complicate or mask other compromises.

Likely exploitation workflow (high level — non-actionable)

1. Attacker discovers the webhook/notification URL (from plugin source, common endpoint naming, or site interaction).
2. Attacker crafts a POST (or GET) to the handler with parameters the plugin expects (order ID, status, amount).
3. Because there is no signature/secret verification, the plugin accepts the payload and updates the order status to paid/completed.
4. Digital goods are delivered automatically, or attacker triggers post-purchase actions (emails, downloads, license activation).
5. Merchants see orders marked paid in WooCommerce without matching transactions in the payment processor account.

Note: Exact exploit payloads and endpoint details are intentionally omitted to avoid enabling abuse.

Business and operational impact

• Financial loss from unpaid digital deliveries and chargebacks.
• Fraud rings may exploit the vulnerability at scale for profit.
• Reputational damage and erosion of customer trust.
• Increased workload for manual reconciliation, refunds, disputes, and audits.
• Potential pivoting to further site compromise when combined with other vulnerabilities.

Detection — signs your site may have been targeted or abused

Audit logs and WooCommerce records for:

• Orders marked “completed” with no matching transaction in your Payeer account.
• Orders completed from IPs outside known payment provider IP ranges.
• Repeated POST requests to unusual endpoints prior to order status changes.
• Automated-looking requests (same user-agent, high frequency) associated with “order paid” events.
• Orders with empty or anomalous customer/payment details.
• Unexpected plugin file changes or new files in wp-content/uploads or plugin directories.

Check WooCommerce order notes — many gateways log raw webhook details there, which can help forensic investigation.

Immediate mitigations (short-term — do this now)

1. Disable the plugin temporarily. This is the safest immediate action — it prevents further unauthenticated callbacks from being processed.
2. If you cannot disable the plugin:
   • Restrict access to the plugin’s notification endpoint using server rules or a WAF: deny all, then allow only trusted processor IP ranges (if available).
   • Add a server-level requirement for an expected secret header/value or block requests that lack a signature parameter.
3. Enforce strict reconciliation: Stop automated fulfillment for orders paid via this gateway. Switch to manual verification until resolved.
4. Review recent orders: Reconcile orders marked as paid by this gateway against the Payeer merchant dashboard. Flag and hold mismatches.
5. Rotate secrets: If plugin-stored API credentials are suspected, rotate those credentials in your merchant account.
6. Monitor logs: Enable detailed access and application logging for at least 30 days and watch for patterns (IP, user-agent, frequency).

WAF / virtual patching guidance (generic)

When a vendor patch is not yet available, a WAF or server-side blocking is an effective short-term control. Below are conceptual ModSecurity-style rules and ideas you can adapt and test in staging before applying to production. Replace example URIs and parameter names with those observed on your site.

Example conceptual ModSecurity rules

# Block POST requests to likely Payeer webhook if signature header missing
SecRule REQUEST_METHOD "POST" "chain,phase:2,deny,status:403,id:1000010,msg:'Block unauthenticated Payeer webhook calls'"
  SecRule REQUEST_URI "@rx /(wp\-content/plugins/crypto-payeer|wc-api=payeer|/wp-json/payeer|/payeer/notify)" "t:none"
  SecRule REQUEST_HEADERS:X-PAYEER-SIGN "!@rx .+"

# Allow only trusted Payeer IPs to reach webhook; otherwise deny (replace ranges)
SecRule REQUEST_URI "@rx /payeer/notify" "phase:1,pass,id:1000020,nolog,ctl:ruleRemoveById=1000010"
SecRule REMOTE_ADDR "!@ipMatch 1.2.3.0/24,2.3.4.0/24" "phase:1,deny,status:403,id:1000021,msg:'Block unknown IP to Payeer notify endpoint'"

# Deny attempts to set order status to completed without a known token
SecRule REQUEST_METHOD "POST" "phase:2,chain,id:1000030,msg:'Block unauthenticated order completion attempt'"
  SecRule ARGS_GET|ARGS_POST|REQUEST_BODY "@rx (status|order_status|pay_status)=(paid|completed|success)" "t:none"
  SecRule ARGS_GET|ARGS_POST|REQUEST_BODY "!@rx (secret|signature|hash|x-payeer-sign)" "t:none"
  SecRule REQUEST_URI "@rx payeer|payeer_notify|wc-api=payeer" "t:none"

# Rate limiting: implement with WAF native rate-limiting features (e.g., 10 req/min per IP)

These rules are illustrative. Test rules carefully to avoid blocking legitimate notifications. If you have a WAF or reverse proxy, use its native rate limiting, IP allowlists, and header validation features to restrict access to webhook endpoints.

Server-level mitigations (Apache/Nginx)

If you cannot use a WAF, apply server-level access controls:

Nginx (example)

location ~* /(wp-content/plugins/crypto-payeer|wc-api=payeer|/wp-json/payeer|/payeer/notify) {
    allow 1.2.3.0/24; # replace with official Payeer IP ranges if available
    deny all;
}

Apache (.htaccess example)

<If "%{REQUEST_URI} =~ m#(wp-content/plugins/crypto-payeer|wc-api=payeer|/wp-json/payeer|/payeer/notify)#">
    Require ip 1.2.3.0/24
    Require all denied
</If>

Alternatively, implement a small middleware that checks for a shared secret header before passing requests to the plugin handler.

Incident response checklist (if you suspect compromise)

1. Isolate: Disable the vulnerable plugin immediately or take the site offline if significant compromise is suspected.
2. Preserve logs: Collect web server access logs, PHP-FPM logs, and WooCommerce logs for the suspected timeframe.
3. Reconcile: Compare all orders marked completed via this gateway with the Payeer merchant account; flag mismatches.
4. Contain: Revoke and rotate credentials related to the plugin/merchant integration; change webhook URLs or enable new secrets.
5. Investigate: Review suspicious orders for IP patterns, user-agent strings, and automation; inspect plugin files for tampering.
6. Remediate: Cancel or hold suspicious orders pending manual verification; restore or rebuild compromised files from clean backups where necessary.
7. Communicate: Notify affected customers if fraudulent access to paid resources occurred; work with the payment processor on disputes.
8. Learn & harden: After containment, deploy WAF rules, strengthen reconciliation procedures, and apply secure development fixes to the plugin.

Developer guidance — how to fix properly

If you maintain the plugin, implement the following fixes and tests:

1. Strict webhook validation: Implement message signing (HMAC) for callbacks. Sign payloads with a merchant secret and verify signatures on every notification. Use timestamps/nonces to prevent replay attacks.
2. Validate payment details: Verify order existence and that amount/currency match. Only mark an order paid after verifying the transaction status with the processor via server-to-server API calls where possible.
3. Authenticate the source: Use IP ranges as a secondary check only; primary verification must be cryptographic.
4. Use proper WooCommerce APIs: Update order state via WooCommerce order APIs and add detailed order notes for traceability.
5. Idempotency and replay protection: Ensure handlers are idempotent and track transaction IDs to prevent reprocessing.
6. Principle of least privilege: Avoid exposing endpoints that modify order state without authorization.
7. Secure coding: Sanitize and validate all inbound parameters; never trust client-controlled values for critical state changes.
8. Testing: Add unit/integration tests that simulate malformed and malicious requests; perform security code reviews and automated scanning.

Detection rules and indicators for security teams

Monitor for:

• Requests with payment parameters (order_id, amount, status) from unusual IPs or user agents.
• Rapid transitions from “pending” to “completed” without corresponding processor transactions.
• High frequency of requests to webhook endpoints with varying order IDs.
• Multiple orders marked completed from the same IP or user-agent in a short window.

Example log searches (conceptual):

• Apache access logs: grep -E “payeer|payeer_notify|wc-api=payeer” access.log
• Search WooCommerce order notes for webhook entries via wp-cli or database queries.
• SIEM: alert when orders marked completed via this gateway exceed a threshold without matching external transactions.

Long-term recommendations for store operators

• Prefer payment plugins that support signed webhooks and cryptographic verification.
• Limit automated fulfillment for new or untested gateways.
• Implement multi-layer fraud detection: device fingerprinting, velocity checks, and manual reviews for high-value items.
• Keep WordPress core, themes, and plugins updated; monitor security advisories.
• Enforce least privilege on admin accounts, enable MFA, and use role separation for staff.

Frequently asked questions

Q: My store doesn’t use the affected plugin. Do I need to worry?

If you do not have the plugin installed and active, you are not directly impacted. However, review all payment integrations to ensure webhook signatures and validations are implemented — this class of vulnerability is common across poorly implemented gateways.

Q: Can I rely on the payment processor to catch fraudulent transactions?

No. A compromised or improperly validated plugin can mark an order as paid in your WooCommerce database even when the payment processor shows no transaction. Always reconcile orders against processor records and require server-side signature verification for trust.

Q: If I disable the plugin, will I still be billed by Payeer?

Disabling the plugin prevents incoming callbacks from being processed on your site. Billing and transactions at the payment processor are independent — reconcile your merchant account separately.

Why virtual patching and WAF matter now

When an official patch is not yet available, virtual patching via a WAF or server rules is the fastest way to lower immediate risk. Virtual patches intercept malicious requests at the edge before they reach vulnerable code. Combined with operational controls (manual reconciliation, holds for high-value orders), this approach buys time for a proper vendor fix and thorough testing.

Action checklist (concise)

1. If the plugin is installed: disable it immediately if possible.
2. If disabling is not possible: restrict access to webhook endpoints (server/WAF), require a shared secret header, and rate-limit traffic.
3. Stop automated fulfillment for orders from this gateway.
4. Reconcile recent orders and investigate anomalies.
5. Rotate integration secrets and webhook endpoints where supported.
6. Collect and preserve logs for forensic review.

Closing thoughts from a Hong Kong security expert

Payment gateway integrations are high-value targets because they can directly trigger fulfillment. A single missing signature or authorization check can let attackers obtain goods and services for free and cause operational chaos. Security is layered: use cryptographic verification for webhooks, enforce reconciliation controls, and apply edge protections (WAF/server rules) when vendor fixes are not immediately available.

Treat CVE-2025-11890 as urgent. If you need site-specific rule drafting or a forensic checklist tuned to your environment, engage a qualified security professional to apply and test controls safely.