CVE-2026-25378: Nelio AB Testing SQL Injection Flaw

CVE-2026-25378 Overview

CVE-2026-25378 is a Blind SQL Injection vulnerability affecting the Nelio AB Testing WordPress plugin. This vulnerability arises from improper neutralization of special elements used in SQL commands (CWE-89), allowing authenticated attackers with high privileges to execute arbitrary SQL queries against the underlying database. The blind nature of this injection means attackers can extract sensitive information through time-based or boolean-based techniques without direct error feedback.

Critical Impact

Authenticated attackers with administrative privileges can exploit this vulnerability to extract sensitive data from the WordPress database, potentially compromising user credentials, session tokens, and other confidential information stored within the application.

Affected Products

• Nelio AB Testing WordPress Plugin versions up to and including 8.2.4
• WordPress installations with vulnerable Nelio AB Testing plugin installed
• All configurations where Nelio AB Testing <= 8.2.4 is active

Discovery Timeline

• 2026-02-19 - CVE-2026-25378 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2026-25378

Vulnerability Analysis

This SQL Injection vulnerability exists within the Nelio AB Testing WordPress plugin, a popular A/B testing solution for WordPress sites. The vulnerability is classified under CWE-89 (Improper Neutralization of Special Elements used in an SQL Command), indicating that user-supplied input is incorporated into SQL queries without proper sanitization or parameterization.

The vulnerability requires network access and high privileges to exploit, but once exploited, it can affect resources beyond the vulnerable component's security scope. The primary impact is on data confidentiality, with potential for limited availability impact. Despite requiring administrative privileges, the cross-scope impact makes this a significant security concern for WordPress installations using the affected plugin.

Root Cause

The root cause of this vulnerability stems from insufficient input validation and improper handling of user-supplied data within SQL query construction. The Nelio AB Testing plugin fails to properly sanitize or parameterize inputs before incorporating them into database queries. This allows specially crafted input containing SQL syntax to be interpreted as part of the query structure rather than as literal data values.

WordPress provides prepared statements through the $wpdb->prepare() method specifically to prevent SQL injection attacks, but this protection appears to have been bypassed or not implemented in the affected code paths.

Attack Vector

The attack vector is network-based, requiring the attacker to have authenticated access with high-level privileges (administrator role). The exploitation process involves:

1. An attacker with administrative access to the WordPress installation navigates to the vulnerable functionality within the Nelio AB Testing plugin
2. The attacker crafts malicious input containing SQL injection payloads designed for blind extraction
3. Since this is a blind SQL injection, the attacker uses time-based or boolean-based techniques to infer data from the database response behavior
4. The attacker systematically extracts sensitive information character by character through conditional queries

As this is a blind SQL injection vulnerability, the attack methodology relies on observing differences in application behavior (response times or boolean conditions) rather than direct data output. Technical details regarding specific exploitation techniques can be found in the Patchstack WordPress Plugin Advisory.

Detection Methods for CVE-2026-25378

Indicators of Compromise

• Unusual or malformed SQL-like strings in plugin-related HTTP request parameters
• Abnormally long response times from the WordPress application indicating time-based SQL injection attempts
• Database query logs showing unexpected SLEEP(), BENCHMARK(), or conditional SQL statements
• Multiple sequential requests with incrementally modified parameters targeting Nelio AB Testing endpoints

Detection Strategies

• Monitor web application firewall (WAF) logs for SQL injection patterns targeting WordPress plugin endpoints
• Implement database query logging and alerting for anomalous query patterns or unauthorized data access
• Review WordPress admin activity logs for suspicious behavior from privileged accounts
• Deploy endpoint detection to identify exploitation attempts through behavioral analysis

Monitoring Recommendations

• Enable detailed logging for the nelio-ab-testing plugin directory and associated database tables
• Configure alerts for SQL injection signatures in HTTP request parameters
• Monitor database performance metrics for unusual query execution patterns
• Audit administrative user sessions for unexpected or automated activity patterns

How to Mitigate CVE-2026-25378

Immediate Actions Required

• Update Nelio AB Testing plugin to a version newer than 8.2.4 when a patched version becomes available
• Review and audit administrative user accounts for signs of compromise
• Implement Web Application Firewall (WAF) rules to block SQL injection attempts
• Consider temporarily disabling the Nelio AB Testing plugin if A/B testing is not critical to operations

Patch Information

The vulnerability affects Nelio AB Testing versions through 8.2.4. Site administrators should monitor for security updates from Nelio Software and apply patches immediately upon release. Detailed advisory information is available from Patchstack WordPress Plugin Advisory.

Workarounds

• Restrict administrative access to trusted users only and implement strong authentication controls
• Deploy a Web Application Firewall with SQL injection detection and blocking capabilities
• Temporarily deactivate the Nelio AB Testing plugin until a security patch is available
• Implement database-level monitoring and access controls to limit the impact of potential exploitation

# WordPress CLI command to deactivate the vulnerable plugin
wp plugin deactivate nelio-ab-testing --allow-root

# Verify plugin status
wp plugin status nelio-ab-testing --allow-root

# Check for available updates
wp plugin update --all --dry-run --allow-root