CVE-2025-8877: AffiliateWP WordPress Plugin SQLi Flaw

CVE-2025-8877 Overview

The AffiliateWP plugin for WordPress is vulnerable to SQL Injection via the ajax_get_affiliate_id_from_login function in all versions up to, and including, 2.28.2. The vulnerability exists due to insufficient escaping on the user-supplied parameter and lack of sufficient preparation on the existing SQL query. This makes it possible for unauthenticated attackers to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database.

Critical Impact

Unauthenticated attackers can extract sensitive information from the WordPress database through SQL injection, potentially compromising user credentials, affiliate data, and other confidential information stored in the database.

Affected Products

• AffiliateWP Plugin for WordPress versions up to and including 2.28.2
• WordPress installations with vulnerable AffiliateWP plugin versions
• Any website using AffiliateWP with the affected AJAX endpoint exposed

Discovery Timeline

• 2025-09-30 - CVE-2025-8877 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2025-8877

Vulnerability Analysis

This SQL Injection vulnerability (CWE-89) affects the ajax_get_affiliate_id_from_login function within the AffiliateWP WordPress plugin. The vulnerability is particularly concerning because it can be exploited by unauthenticated attackers, meaning no login credentials are required to launch an attack.

The vulnerable function processes user-supplied input without properly sanitizing or parameterizing the data before incorporating it into SQL queries. WordPress provides the $wpdb->prepare() method specifically to prevent SQL injection by properly escaping and preparing SQL statements, but this function fails to adequately implement these protections.

The network-accessible attack vector combined with low attack complexity makes this vulnerability relatively easy to exploit. While the vulnerability impacts confidentiality by allowing data extraction, it does not directly allow modification of data or denial of service.

Root Cause

The root cause of this vulnerability is twofold:

1. Insufficient Input Escaping: User-supplied parameters passed to the ajax_get_affiliate_id_from_login function are not properly escaped before being used in database queries.

2. Lack of Prepared Statements: The existing SQL query does not utilize WordPress's $wpdb->prepare() function or equivalent parameterized query mechanisms to safely handle user input.

This combination allows malicious SQL code injected through user input to be executed as part of the database query, enabling attackers to manipulate the query logic and extract unauthorized data.

Attack Vector

The attack can be executed remotely over the network without any authentication requirements. An attacker would target the AJAX endpoint associated with the ajax_get_affiliate_id_from_login function, crafting malicious requests that include SQL injection payloads in the vulnerable parameter.

The vulnerability enables blind or error-based SQL injection techniques, allowing attackers to systematically extract database contents including user credentials, affiliate information, payment details, and potentially WordPress administrator accounts. Since WordPress stores user passwords as hashes, attackers would need to perform offline cracking to obtain plaintext passwords, but email addresses and other sensitive data would be immediately accessible.

For detailed technical information about this vulnerability, refer to the Wordfence Vulnerability Report.

Detection Methods for CVE-2025-8877

Indicators of Compromise

• Unusual or malformed requests to WordPress AJAX endpoints containing SQL syntax characters such as single quotes, UNION statements, or comment sequences
• Database query logs showing unexpected SELECT statements or UNION-based queries originating from the AffiliateWP plugin
• Error logs containing SQL syntax errors related to the ajax_get_affiliate_id_from_login function
• Suspicious traffic patterns targeting /wp-admin/admin-ajax.php with AffiliateWP-related action parameters

Detection Strategies

• Deploy Web Application Firewall (WAF) rules to detect and block SQL injection patterns in requests to WordPress AJAX endpoints
• Monitor HTTP request logs for common SQL injection signatures including UNION SELECT, OR 1=1, encoded SQL characters, and time-based blind injection attempts
• Implement database activity monitoring to detect anomalous query patterns or bulk data extraction attempts
• Use intrusion detection systems (IDS) with signatures for WordPress-specific SQL injection attacks

Monitoring Recommendations

• Enable detailed logging for WordPress AJAX requests and review logs regularly for suspicious patterns
• Configure alerts for multiple failed or malformed requests to the affected endpoint from single IP addresses
• Monitor database performance metrics for unusual query execution times that may indicate blind SQL injection attempts
• Review web server access logs for requests containing URL-encoded SQL injection payloads

How to Mitigate CVE-2025-8877

Immediate Actions Required

• Update AffiliateWP plugin to a version newer than 2.28.2 that addresses this vulnerability
• If immediate update is not possible, temporarily disable the AffiliateWP plugin until patching is complete
• Implement WAF rules to block SQL injection attempts targeting the vulnerable endpoint
• Review database access logs for evidence of prior exploitation and consider database credential rotation if compromise is suspected
• Perform a security audit of WordPress installations to identify any unauthorized data access

Patch Information

Update the AffiliateWP plugin to the latest available version through the WordPress admin dashboard or by downloading directly from the AffiliateWP website. Ensure all WordPress plugins are kept up to date and regularly monitored for security advisories.

After updating, verify the patch has been applied by checking the plugin version number in the WordPress plugins administration page. Review the Wordfence Vulnerability Report for additional remediation guidance.

Workarounds

• Implement a Web Application Firewall with SQL injection detection rules to filter malicious requests before they reach the application
• Restrict access to WordPress AJAX endpoints at the web server level using IP whitelisting where feasible
• Consider disabling AJAX functionality in AffiliateWP temporarily if not essential for business operations
• Deploy network-level intrusion prevention systems to detect and block exploitation attempts

# Example .htaccess rule to block common SQL injection patterns
# Add to WordPress root .htaccess file as temporary mitigation
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{QUERY_STRING} [^a-z](union|select|insert|drop|update|delete|concat|char|declare)[^a-z] [NC]
RewriteRule .* - [F,L]
</IfModule>