CVE-2026-3309: ProfilePress WordPress Plugin RCE Vulnerability

CVE-2026-3309 Overview

The ProfilePress plugin for WordPress (also known as Paid Membership Plugin, Ecommerce, User Registration Form, Login Form, User Profile & Restrict Content) is vulnerable to arbitrary shortcode execution in all versions up to and including 4.16.11. This vulnerability arises because the plugin allows user-supplied billing field values from the checkout process to be interpolated into shortcode template strings that are subsequently processed without proper sanitization of shortcode syntax. This enables unauthenticated attackers to execute arbitrary shortcodes by submitting crafted billing field values during the checkout process.

Critical Impact

Unauthenticated attackers can execute arbitrary WordPress shortcodes by injecting malicious values into billing fields during checkout, potentially leading to information disclosure or site manipulation.

Affected Products

• ProfilePress WordPress Plugin versions up to and including 4.16.11
• WordPress sites utilizing ProfilePress checkout functionality
• Sites with third-party shortcode-enabled plugins that may be chained with this vulnerability

Discovery Timeline

• April 4, 2026 - CVE-2026-3309 published to NVD
• April 7, 2026 - Last updated in NVD database

Technical Details for CVE-2026-3309

Vulnerability Analysis

This vulnerability is classified as CWE-94 (Improper Control of Generation of Code - Code Injection). The ProfilePress plugin fails to properly sanitize user input within billing field values during the checkout process. When a user submits billing information, the plugin interpolates these values into shortcode template strings. Because the plugin does not strip or escape shortcode syntax (square bracket notation), an attacker can inject arbitrary shortcode tags that WordPress will subsequently execute.

The attack requires no authentication, as the checkout process is typically accessible to all site visitors. An attacker can leverage this vulnerability to execute any shortcode registered on the WordPress installation, including those from other plugins that may expose sensitive functionality such as database queries, file operations, or administrative actions.

Root Cause

The root cause lies in the plugin's shortcode template processing mechanism. When constructing dynamic content from billing fields, the plugin directly concatenates user-controlled input into template strings that are later passed to WordPress's do_shortcode() function. The absence of input sanitization specifically targeting shortcode bracket syntax ([ and ]) allows attackers to break out of the intended context and inject their own shortcode directives.

Attack Vector

The attack is network-accessible and requires no privileges or user interaction. An attacker initiates the attack by navigating to a checkout page on a vulnerable WordPress site and submitting billing field values containing malicious shortcode syntax. For example, an attacker might input a crafted string in a billing address field that includes shortcode tags. When the plugin processes this data and renders content using the template system, the injected shortcodes are executed with the privileges of the web server.

The vulnerability becomes particularly dangerous when combined with other plugins that register powerful shortcodes for administrative functions, potentially escalating the impact to arbitrary code execution or sensitive data exfiltration.

Detection Methods for CVE-2026-3309

Indicators of Compromise

• Unusual billing field values in checkout submissions containing square bracket characters [ and ]
• Checkout form submissions with shortcode-like syntax such as [shortcode_name] in address or name fields
• Unexpected shortcode execution logs or plugin activity triggered during checkout processing
• Web application firewall (WAF) alerts for injection patterns in form submissions

Detection Strategies

• Monitor checkout form submissions for input containing WordPress shortcode syntax patterns
• Implement WAF rules to detect and block square bracket injection attempts in billing fields
• Review ProfilePress plugin logs for anomalous shortcode processing events
• Scan access logs for unusual POST requests to checkout endpoints with suspicious payloads

Monitoring Recommendations

• Configure real-time alerting for injection patterns in form submissions to checkout endpoints
• Enable detailed logging for the ProfilePress plugin to capture billing field processing events
• Deploy endpoint detection and response (EDR) solutions to identify post-exploitation activity
• Establish baseline behavior for checkout processes to detect statistical anomalies

How to Mitigate CVE-2026-3309

Immediate Actions Required

• Update ProfilePress plugin to a version newer than 4.16.11 immediately
• Review recent checkout submissions for evidence of exploitation attempts
• Temporarily disable the ProfilePress checkout functionality if an immediate update is not possible
• Audit installed plugins for shortcodes that could be abused if executed via this vulnerability

Patch Information

A security patch addressing this vulnerability is available through the WordPress plugin repository. The fix involves proper sanitization of billing field values before shortcode template interpolation. Review the WordPress Plugin Changeset for technical details on the remediation. Additional vulnerability information is available in the Wordfence Vulnerability Report.

Workarounds

• Implement WAF rules to strip or reject input containing shortcode bracket syntax in checkout fields
• Use input validation at the web server level to sanitize billing field submissions before they reach WordPress
• Consider temporarily disabling external checkout access until the plugin can be updated
• Deploy virtual patching through a WordPress security plugin to filter malicious input

# Example WAF rule concept for ModSecurity to block shortcode injection
SecRule ARGS "@rx \[.+\]" "id:100001,phase:2,deny,status:403,msg:'Potential shortcode injection attempt blocked'"