CVE-2025-6688: Idokd Simple Payment Auth Bypass Flaw

CVE-2025-6688 Overview

The Simple Payment plugin for WordPress contains a critical authentication bypass vulnerability affecting versions 1.3.6 through 2.3.8. The flaw exists due to improper identity verification in the create_user() function, allowing unauthenticated attackers to bypass authentication mechanisms and gain administrative access to WordPress installations running the vulnerable plugin.

Critical Impact

Unauthenticated remote attackers can bypass authentication and log in as administrative users, potentially gaining complete control over affected WordPress sites.

Affected Products

• Idokd Simple Payment plugin versions 1.3.6 to 2.3.8
• WordPress installations with vulnerable Simple Payment plugin versions

Discovery Timeline

• 2025-06-27 - CVE-2025-6688 published to NVD
• 2025-07-02 - Last updated in NVD database

Technical Details for CVE-2025-6688

Vulnerability Analysis

This authentication bypass vulnerability (CWE-288: Authentication Bypass Using an Alternate Path or Channel) stems from a fundamental flaw in how the Simple Payment plugin handles user authentication. The plugin fails to properly verify a user's identity before granting access through the create_user() function, creating a critical security gap that allows unauthenticated attackers to assume administrative privileges.

The vulnerability is particularly severe because it requires no authentication, can be exploited remotely over the network, and requires no user interaction. Successful exploitation grants attackers full administrative access, compromising the confidentiality, integrity, and availability of the affected WordPress installation.

Root Cause

The root cause lies in insufficient identity verification within the create_user() function. The plugin does not implement proper authentication checks before allowing user login operations, enabling attackers to bypass the normal authentication flow entirely. This represents a classic authentication bypass pattern where an alternate code path circumvents intended security controls.

Attack Vector

The attack vector is network-based, meaning attackers can exploit this vulnerability remotely without requiring any prior authentication or user interaction. The attack complexity is low, making it accessible to attackers with minimal technical sophistication. An attacker would target the create_user() function endpoint to establish an authenticated session as an administrative user without providing valid credentials.

The exploitation process involves sending specially crafted requests to the vulnerable function, which fails to validate the requester's identity before granting elevated access. This allows direct escalation to administrative privileges on the WordPress installation.

Detection Methods for CVE-2025-6688

Indicators of Compromise

• Unexpected administrative user sessions or login events without corresponding authentication logs
• Unusual activity in WordPress admin panel from unrecognized IP addresses
• Suspicious calls to the Simple Payment plugin's user creation endpoints
• New administrator accounts created without legitimate administrative action

Detection Strategies

• Monitor WordPress authentication logs for login events that bypass standard authentication flows
• Implement web application firewall (WAF) rules to detect unusual requests targeting the Simple Payment plugin
• Review access logs for requests to plugin endpoints associated with user creation functions
• Deploy file integrity monitoring to detect unauthorized changes following potential exploitation

Monitoring Recommendations

• Enable comprehensive logging for all WordPress authentication events
• Configure alerts for administrative login events from unknown or suspicious IP addresses
• Monitor for anomalous user creation or privilege escalation activities
• Regularly audit the list of WordPress administrator accounts for unauthorized additions

How to Mitigate CVE-2025-6688

Immediate Actions Required

• Update the Simple Payment plugin to version 2.3.9 or later immediately
• Audit all existing WordPress administrator accounts for unauthorized entries
• Review recent login activity and access logs for signs of exploitation
• Consider temporarily disabling the plugin if immediate patching is not possible

Patch Information

The vendor has released a security patch in version 2.3.9 of the Simple Payment plugin. The patch addresses the authentication bypass by implementing proper identity verification in the create_user() function. Technical details of the fix can be reviewed in the WordPress Plugin Change Log. Additional vulnerability information is available in the Wordfence Vulnerability Report.

Workarounds

• Disable the Simple Payment plugin until the patched version can be applied
• Implement IP-based access restrictions to the WordPress admin panel
• Deploy web application firewall rules to block suspicious requests to plugin endpoints
• Enable two-factor authentication for all administrative accounts as an additional security layer

# WordPress CLI command to update the Simple Payment plugin
wp plugin update simple-payment

# Verify the installed version after update
wp plugin get simple-payment --field=version