CVE-2025-26978: FS Poster SQLi Vulnerability

CVE-2025-26978 Overview

CVE-2025-26978 is a SQL Injection vulnerability in the FS Poster WordPress plugin developed by fs-code. The flaw affects all versions of FS Poster up to and including 6.5.8. An authenticated attacker with low privileges can submit crafted input that is concatenated into SQL statements without proper neutralization of special elements [CWE-89]. Successful exploitation allows attackers to read database contents, manipulate query logic, and impact site availability through the WordPress database backend. The issue is tracked under the network attack vector and requires no user interaction.

Critical Impact
Authenticated attackers can inject arbitrary SQL into the WordPress database, exposing sensitive data and degrading site availability across all sites running FS Poster <= 6.5.8.

Affected Products

fs-code FS Poster plugin for WordPress
All versions from n/a through <= 6.5.8
WordPress sites with FS Poster installed and activated

Discovery Timeline

2025-03-15 - CVE-2025-26978 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-26978

Vulnerability Analysis

The FS Poster plugin fails to properly neutralize special elements in user-supplied input before incorporating that input into SQL statements. The vulnerability is classified under [CWE-89] Improper Neutralization of Special Elements used in an SQL Command. Attackers authenticated to a WordPress instance with low-privilege accounts can deliver malicious payloads through plugin-handled parameters. Because the issue produces a scope change, exploitation impacts data and components beyond the vulnerable plugin itself.

The network-reachable nature of the flaw and low complexity of exploitation make it suitable for automated scanning campaigns targeting WordPress sites. Confidentiality impact is high while availability impact is low, indicating the primary risk is data disclosure from the WordPress database, including user credentials, session tokens, and stored content.

Root Cause

The root cause is the construction of SQL queries through string concatenation or insufficient sanitization of input parameters supplied to FS Poster endpoints. The plugin does not consistently use $wpdb->prepare() with proper placeholder binding, allowing attacker-controlled values to alter query structure rather than acting as data.

Attack Vector

An attacker first obtains low-privilege authenticated access to the target WordPress site, such as a Subscriber or Contributor account. The attacker then sends HTTP requests containing SQL metacharacters to plugin endpoints exposed by FS Poster. The malicious input flows into a database query where it modifies the query logic, enabling union-based extraction, boolean-based inference, or time-based blind injection. The vulnerability mechanism is documented in the Patchstack SQL Injection Vulnerability advisory.

Detection Methods for CVE-2025-26978

Indicators of Compromise

HTTP requests to FS Poster plugin endpoints containing SQL metacharacters such as ', UNION SELECT, SLEEP(, or -- in parameter values
Unusual wp_users or wp_options table reads originating from PHP-FPM worker processes tied to plugin requests
Spikes in 500-class HTTP responses from URLs under /wp-admin/admin-ajax.php or /wp-json/ paths invoking FS Poster actions
New or modified administrator accounts not created by legitimate workflows

Detection Strategies

Inspect WordPress and web server access logs for FS Poster parameter values containing encoded SQL syntax or oversized payloads
Enable MySQL general query logging temporarily and correlate suspicious queries with plugin-handled HTTP requests
Deploy a Web Application Firewall (WAF) rule set that flags SQL injection patterns targeting plugin endpoints

Monitoring Recommendations

Alert on authenticated low-privilege users issuing repeated requests to FS Poster admin-ajax actions
Monitor database query duration outliers that may indicate time-based blind SQL injection
Track plugin file integrity and WordPress role changes to detect post-exploitation persistence

How to Mitigate CVE-2025-26978

Immediate Actions Required

Update the FS Poster plugin to a version later than 6.5.8 once the vendor releases a fix
Audit existing WordPress user accounts and revoke unnecessary low-privilege access
Rotate WordPress secret keys, database credentials, and administrator passwords if exploitation is suspected
Restrict access to FS Poster endpoints using IP allowlists or authentication proxies where feasible

Patch Information

Review the Patchstack advisory for CVE-2025-26978 for the latest patched release. Apply updates through the WordPress plugin manager or WP-CLI as soon as a fixed version is available. If a patch is not yet available, deactivate and remove the FS Poster plugin until remediation is published.

Workarounds

Deactivate the FS Poster plugin until a patched version is installed
Deploy WAF rules that block SQL injection signatures on plugin URLs
Limit account registration and require email verification to reduce the pool of low-privilege attackers
Apply database least-privilege by ensuring the WordPress MySQL user lacks FILE and SUPER privileges

bash

# Configuration example: temporarily deactivate the plugin via WP-CLI
wp plugin deactivate fs-poster
wp plugin status fs-poster