CVE-2025-58801: KCS Responder CSRF Vulnerability

CVE-2025-58801 Overview

CVE-2025-58801 is a Cross-Site Request Forgery (CSRF) vulnerability affecting the KCS Responder plugin for WordPress. The flaw impacts all versions up to and including 4.3.8. An attacker can craft a malicious web page that triggers unauthorized state-changing requests when an authenticated victim visits it. Successful exploitation requires user interaction but no authentication on the attacker's side. The issue is tracked under CWE-352.

Critical Impact
Attackers can trick authenticated WordPress users into executing unintended state-changing actions in the Responder plugin, leading to limited integrity and availability impact on the affected site.

Affected Products

KCS Responder WordPress plugin, versions up to and including 4.3.8
WordPress sites running the vulnerable Responder plugin
Administrator and privileged user sessions on affected WordPress installations

Discovery Timeline

2025-09-05 - CVE-2025-58801 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-58801

Vulnerability Analysis

The Responder plugin fails to validate the origin of state-changing HTTP requests. The plugin does not implement or does not correctly verify anti-CSRF tokens (WordPress nonces) on sensitive endpoints. An attacker who lures an authenticated user to a controlled page can force the browser to submit requests that the plugin processes as legitimate.

The attack requires user interaction, such as clicking a link or loading an attacker-controlled page. Exploitation occurs across origins without prior authentication by the attacker. Impact is limited to integrity and availability of resources managed by the plugin, with no direct data confidentiality loss reported.

The EPSS probability is 0.127%, reflecting a low observed likelihood of exploitation activity at this time.

Root Cause

The root cause is missing or improperly implemented CSRF protection on request handlers within the Responder plugin. WordPress provides wp_nonce_field() and check_admin_referer() primitives to mitigate CSRF, but the vulnerable code paths in versions through 4.3.8 do not enforce these checks consistently.

Attack Vector

The attack vector is network-based and leverages the victim's authenticated session. An attacker hosts a malicious page containing an auto-submitting form or an image tag pointing at a vulnerable plugin endpoint. When a logged-in WordPress user visits the page, the browser attaches session cookies, and the plugin processes the forged request. See the Patchstack WordPress Vulnerability Advisory for advisory details.

Detection Methods for CVE-2025-58801

Indicators of Compromise

Unexpected configuration changes within the Responder plugin admin interface
HTTP POST requests to Responder plugin endpoints with Referer headers pointing to external domains
Administrative actions logged during periods of user browsing activity unrelated to plugin management

Detection Strategies

Inspect web server access logs for state-changing requests to Responder plugin URLs originating from cross-origin referrers
Enable WordPress audit logging to correlate plugin setting changes with authenticated session activity
Review browser and endpoint telemetry for outbound connections to suspicious domains preceding plugin state changes

Monitoring Recommendations

Alert on POST requests to /wp-admin/admin.php?page=responder* and /wp-admin/admin-ajax.php handlers lacking valid nonce parameters
Monitor for anomalous administrator session behavior, including plugin configuration changes outside routine maintenance windows
Correlate WordPress access logs with endpoint activity to identify user-initiated visits to attacker-controlled pages

How to Mitigate CVE-2025-58801

Immediate Actions Required

Update the KCS Responder plugin to a version newer than 4.3.8 as soon as a patched release becomes available
Restrict administrator access to trusted networks and enforce short session lifetimes for privileged WordPress accounts
Educate administrators to log out of WordPress before browsing untrusted sites

Patch Information

At the time of publication, no fixed version is listed in the enriched advisory data. Monitor the Patchstack WordPress Vulnerability Advisory and the plugin vendor's channels for a patched release addressing CVE-2025-58801.

Workarounds

Temporarily deactivate the Responder plugin until a patched version is released
Deploy a Web Application Firewall (WAF) rule to block cross-origin POST requests targeting Responder plugin endpoints
Enforce SameSite=Strict or SameSite=Lax cookie attributes on WordPress authentication cookies where compatible

bash

# Example WAF rule concept to block cross-origin requests to the Responder plugin
# ModSecurity-style pseudo-rule
SecRule REQUEST_URI "@contains /wp-admin/admin.php" \
  "chain,deny,status:403,id:1005801,msg:'Blocked cross-origin request to Responder plugin'"
SecRule ARGS:page "@rx ^responder" "chain"
SecRule REQUEST_HEADERS:Referer "!@beginsWith https://your-wordpress-site.example/"