Simple Membership Vulnerability – Reflected Cross-Site Scripting Vulnerability via environment_mode – CVE-2023-6882 | WordPress Plugin Vulnerability Report

Plugin Name: Simple Membership

Key Information:

  • Software Type: Plugin
  • Software Slug: simple-membership
  • Software Status: Active
  • Software Author: mra13
  • Software Downloads: 2,315,432
  • Active Installs: 50,000
  • Last Updated: December 18, 2023
  • Patched Versions: 4.3.9
  • Affected Versions: <= 4.3.8

Vulnerability Details:

  • Name: Simple Membership <= 4.3.8 - Reflected Cross-Site Scripting Vulnerability via environment_mode
  • Type: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
  • CVE: CVE-2023-6882
  • CVSS Score: 6.1 (Medium)
  • Publicly Published: December 18, 2023
  • Researcher: Rein Daelman
  • Description: The Simple Membership plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the ‘environment_mode’ parameter in all versions up to, and including, 4.3.8 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link.


The Simple Membership for WordPress has a vulnerability in versions up to and including 4.3.8 that allows for Reflected Cross-Site Scripting via the 'environment_mode' parameter. This vulnerability has been patched in version 4.3.9.

Detailed Overview:

The Simple Membership plugin did not properly sanitize or escape user input from the 'environment_mode' parameter before outputting it back in the application response. This allowed attackers to inject malicious scripts that would execute in a victim's browser when they visit a crafted link. The vulnerability is rated as medium severity with a CVSS score of 6.1. It was publicly disclosed by the researcher Rein Daelman on December 18, 2023. Successful exploitation could allow attackers to perform actions on behalf of victims or steal sensitive information from their browsers.

Advice for Users:

  1. Immediate Action: Users should update to version 4.3.9 as soon as possible.
  2. Check for Signs of Vulnerability: Review server logs for any suspicious requests involving the 'environment_mode' parameter.
  3. Alternate Plugins: Consider using MemberPress or Paid Memberships Pro for membership functionality.
  4. Stay Updated: Enable automatic updates in WordPress to receive security fixes when available.


This reflected XSS in Simple Membership serves as an important reminder for users to keep all plugins updated. Developers also must ensure proper validation and escaping of parameters. The prompt patch release indicates the plugin author is committed to fixing vulnerabilities, but users should still consider whether an alternative membership plugin with a better security track record may be warranted.


Detailed Report:

Keeping your WordPress website and its plugins up-to-date is critical for security. Unfortunately, too often vulnerabilities arise that put sites at risk until patches are available. This is the case with a recently uncovered reflected cross-site scripting (XSS) flaw in the popular Simple Membership plugin, active on over 50,000 sites. Versions up to and including 4.3.8 are affected, allowing attackers to potentially inject malicious JavaScript if site visitors can be tricked into clicking on a specially crafted link.

Successful exploitation could enable stealing visitor data or performing actions with their permissions. While the developer has now patched the problem in version 4.3.9, users of older releases remain in danger. Updating immediately is highly recommended.

For background, Simple Membership is a widely-used WordPress membership plugin with over 2 million downloads. It allows site owners to offer premium content or experiences to logged-in members. The plugin is actively maintained and updated.

However, this recent reflected XSS vulnerability arises from insufficient sanitization of the “environment_mode” parameter that is passed back and forth between the site and user’s browser. By injecting malicious JavaScript into this parameter, attackers could compromise victims who visit a link carrying this payload. The flaw enables cross-site scripting attacks ranked at medium severity per the common vulnerability scoring system (CVSS).

Impacts if exploited could include account takeover, data extraction, or forcing actions on victim sites. Furthermore, this type of vulnerability opens the door for other attacks like phishing or malware injection. There have already been 14 previous vulnerabilities found in Simple Membership since 2016, underscoring the security risks of relying on complex plugin code.

Updating to Simple Membership version 4.3.9 patches this particular flaw by properly escaping the vulnerable parameter. However, the broader issue remains – as a small business owner dependent on your website, you cannot realistically stay on top of monitoring all plugins for vulnerabilities as they are discovered. Yet allowing known flaws to persist puts your business at risk.

Consider proactively having your site assessed for security gaps on a regular basis. Ethical hacking simulations can uncover risks before criminals find them. Prioritizing ongoing security checks is the best way to protect your business as threats continue evolving. Don’t wait until after an incident occurs – make robust website security central to your online operations from day one.

As a business owner, you don't have time to constantly monitor for WordPress vulnerabilities like this. At Your WP Guy, we become your outsourced IT team to handle security, updates, maintenance and support. Let us fully audit your site and plugins to assess any impact from this issue. We'll update everything to patched versions so you can rest easy knowing your site is locked down.

Focus on your business goals while we focus on your WordPress site's security. Chat with us anytime during business hours, schedule a call or call 678-995-5169 for a free consultation on securing your online presence.

Simple Membership Vulnerability – Reflected Cross-Site Scripting Vulnerability via environment_mode – CVE-2023-6882 | WordPress Plugin Vulnerability Report FAQs

Leave a Comment