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CVE-2026-19804 — The s2Member – Excellent for All Kinds of Memberships, Content Restriction Paywalls &…

Key facts

CVE-2026-19804 is a High (8.8) vulnerability: The s2Member – Excellent for All Kinds of Memberships, Content Restriction Paywalls &…. This entry ships a detection-only PoC and a Docker test lab.
CVE CVE-2026-19804
Severity High (8.8)
Detection / prevention —
PoC poc.py
Source 2026/CVE-2026-19804/

Details

English | 한국어

Description

The s2Member – Excellent for All Kinds of Memberships, Content Restriction Paywalls & Member Access Subscriptions plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 260814 via the 'first_name' parameter parameter. This is due to insufficient sanitization of the first_name parameter via esc_refs(), which strips only regex backreferences and not PHP tags, before substitution into the eval'd Signup Tracking Codes template, combined with disclosure of the site-global proxy verification key that allows PayPal postback verification to be bypassed. This makes it possible for unauthenticated attackers to execute code on the server. Successful exploitation requires that the site administrator has configured a Signup Tracking Codes template containing the %%first_name%% placeholder (a documented, GUI-supported feature) and that the attacker has obtained the site-global proxy verification key, which is exposed in plaintext in the JSON response of any PayPal Checkout AJAX request on the target site.

Vulnerability Details

Property Value
CVE ID CVE-2026-19804
Type RCE
CVSS Score 8.8

Proof of Concept

Download

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-19804/poc.py

Usage

# Run PoC against target
python3 poc.py --target <TARGET_URL>

# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>

⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.

Test Lab

This repository includes a Docker-based test environment with both vulnerable and patched applications.

Quick Start

# Clone and navigate to CVE directory
cd CVE-2026-19804

# Start both applications
docker-compose up -d

# Run tests
./run-tests.sh    # Linux/Mac
./run-tests.ps1   # Windows PowerShell

Application Endpoints

Application URL Status
Vulnerable App http://localhost:8080 Shows vulnerability
Patched App http://localhost:8081 Demonstrates fix

Directory Structure

├── README.md           # English documentation
├── README_KO.md        # Korean documentation
├── poc.py              # PoC detection script
├── docker-compose.yml  # Container orchestration
├── run-tests.sh        # Linux/Mac test runner
├── run-tests.ps1       # Windows test runner
├── vulnerable-app/     # Vulnerable version
│   ├── app.py
│   ├── Dockerfile
│   └── requirements.txt
└── patched-app/        # Fixed version
    ├── app.py
    ├── Dockerfile
    └── requirements.txt

References

  • https://plugins.trac.wordpress.org/browser/s2member/trunk/src/includes/classes/paypal-checkout-in.inc.php#L736
  • https://plugins.trac.wordpress.org/browser/s2member/trunk/src/includes/classes/paypal-return-in-subscr-or-wa-w-level.inc.php#L311
  • https://plugins.trac.wordpress.org/browser/s2member/trunk/src/includes/classes/paypal-return-in-subscr-or-wa-w-level.inc.php#L319
  • https://plugins.trac.wordpress.org/browser/s2member/trunk/src/includes/classes/paypal-return-in.inc.php#L47
  • https://plugins.trac.wordpress.org/browser/s2member/trunk/src/includes/classes/paypal-utilities.inc.php#L185
  • https://plugins.trac.wordpress.org/browser/s2member/trunk/src/includes/classes/paypal-utilities.inc.php#L92
  • https://plugins.trac.wordpress.org/browser/s2member/trunk/src/includes/classes/tracking-codes.inc.php#L71
  • https://plugins.trac.wordpress.org/browser/s2member/trunk/src/includes/classes/utilities.inc.php#L49
  • https://plugins.trac.wordpress.org/changeset?reponame=&old=3671073%40s2member&new=3671073%40s2member
  • https://www.wordfence.com/threat-intel/vulnerabilities/id/e87da8fa-04cc-4b9a-9dde-be7d4f2bd76e?source=cve

Generated by PoC Generator on 2026-09-26T23:08:16.648877103

Frequently asked questions

What is CVE-2026-19804?

CVE-2026-19804 is a High (8.8) vulnerability: The s2Member – Excellent for All Kinds of Memberships, Content Restriction Paywalls &…. This entry ships a detection-only PoC and a Docker test lab.

How do I detect CVE-2026-19804?

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2026-19804?

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

For authorized security testing and research only. See the full source and NVD record.