CVE-2026-39475: User Feedback SQL Injection Vulnerability

CVE-2026-39475 Overview

CVE-2026-39475 is a Blind SQL Injection vulnerability affecting the User Feedback plugin (userfeedback-lite) for WordPress, developed by Syed Balkhi. This vulnerability allows attackers to inject malicious SQL commands through improperly neutralized special elements, potentially enabling unauthorized access to sensitive database information without direct output visibility.

Critical Impact

Attackers can exploit this blind SQL injection to extract sensitive data from WordPress databases, including user credentials, personal information, and other confidential data stored in the affected installation.

Affected Products

• User Feedback (userfeedback-lite) plugin versions through 1.10.1
• WordPress installations running vulnerable versions of the plugin

Discovery Timeline

• 2026-04-08 - CVE-2026-39475 published to NVD
• 2026-04-08 - Last updated in NVD database

Technical Details for CVE-2026-39475

Vulnerability Analysis

This vulnerability is classified as CWE-89: Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection'). The User Feedback plugin fails to properly sanitize user-supplied input before incorporating it into SQL queries, creating an exploitable condition for blind SQL injection attacks.

Blind SQL injection differs from standard SQL injection in that the attacker cannot directly see the results of the injected query in the application's response. Instead, attackers must infer information based on the application's behavior, such as response times (time-based blind SQLi) or conditional responses (boolean-based blind SQLi). This technique, while more complex to execute, can still lead to complete database compromise.

Root Cause

The root cause of this vulnerability lies in insufficient input validation and sanitization within the User Feedback plugin's database interaction layer. User-controlled input is directly concatenated or interpolated into SQL queries without proper parameterization or escaping, allowing specially crafted input to alter the intended SQL command structure.

WordPress provides secure database abstraction methods through the $wpdb class, including prepared statements via $wpdb->prepare(). The vulnerable code path in the User Feedback plugin likely bypasses these protective mechanisms, directly incorporating untrusted data into query strings.

Attack Vector

The attack vector for this vulnerability involves submitting specially crafted input through the User Feedback plugin's data collection mechanisms. An attacker can inject SQL syntax that, while not returning visible output, modifies query behavior in detectable ways.

Exploitation typically follows a methodical approach where the attacker sends payloads that cause the database to perform conditional operations. For boolean-based attacks, the injected SQL evaluates true or false conditions, with different application responses indicating the result. For time-based attacks, SQL sleep functions or heavy computations are injected, with response delays confirming successful injection.

The attacker can systematically extract database contents character by character, eventually reconstructing complete database records including sensitive user data and authentication credentials.

Detection Methods for CVE-2026-39475

Indicators of Compromise

• Unusual SQL query patterns in WordPress database logs containing blind injection techniques
• Abnormally slow database responses indicating time-based SQLi attempts
• Multiple requests to User Feedback plugin endpoints with suspicious parameter values
• Database error logs showing malformed query attempts or SQL syntax errors

Detection Strategies

• Monitor web application firewall (WAF) logs for SQL injection patterns targeting the userfeedback-lite plugin
• Implement database query logging and analyze for anomalous query structures
• Review WordPress access logs for repeated requests with varying payload parameters characteristic of blind SQLi enumeration
• Deploy intrusion detection rules targeting common blind SQL injection syntax patterns

Monitoring Recommendations

• Enable verbose database logging to capture query execution times and identify time-based injection attempts
• Configure WordPress security plugins to alert on suspicious activity involving the User Feedback plugin
• Implement real-time monitoring of database query performance for unexpected execution delays
• Set up alerts for failed authentication attempts following potential credential extraction

How to Mitigate CVE-2026-39475

Immediate Actions Required

• Verify your installed version of User Feedback (userfeedback-lite) by checking the WordPress plugin dashboard
• If running version 1.10.1 or earlier, consider temporarily deactivating the plugin until a patch is available
• Review database logs for any suspicious activity that may indicate prior exploitation attempts
• Implement web application firewall rules to filter SQL injection attempts targeting this plugin

Patch Information

Organizations should monitor the Patchstack vulnerability database for patch release announcements. Update to the latest version of the User Feedback plugin as soon as a security update is made available by the vendor.

Workarounds

• Temporarily disable the User Feedback plugin until a patched version is released
• Implement WAF rules to block common SQL injection patterns in requests to the plugin's endpoints
• Restrict access to WordPress admin and plugin functionality to trusted IP addresses where possible
• Consider using database-level security controls to limit the plugin's database user permissions

# WordPress CLI command to deactivate the vulnerable plugin
wp plugin deactivate userfeedback-lite

# Verify plugin status
wp plugin status userfeedback-lite

# Check for available updates
wp plugin update userfeedback-lite --dry-run