CVE-2025-9895: Notification Bar Plugin CSRF Vulnerability

CVE-2025-9895 Overview

The Notification Bar plugin for WordPress contains a Cross-Site Request Forgery (CSRF) vulnerability affecting all versions up to and including 2.2. The flaw resides in the subscriber-list-empty.php file, which lacks proper nonce validation. Unauthenticated attackers can craft malicious requests that empty the plugin's subscriber list. Exploitation requires tricking a site administrator into clicking a crafted link or visiting an attacker-controlled page while authenticated to WordPress. The vulnerability is classified under CWE-352 (Cross-Site Request Forgery).

Critical Impact
Successful exploitation allows unauthenticated attackers to delete the entire subscriber list of an affected WordPress site by leveraging an authenticated administrator's session.

Affected Products

Notification Bar plugin for WordPress (slug: simple-bar)
All versions up to and including 2.2
WordPress sites with the plugin installed and an authenticated administrator

Discovery Timeline

2025-10-03 - CVE-2025-9895 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-9895

Vulnerability Analysis

The Notification Bar plugin exposes an administrative action through the subscriber-list-empty.php script. This script performs a destructive operation, clearing the stored subscriber list, without verifying the request's authenticity. WordPress provides a nonce mechanism (wp_verify_nonce, check_admin_referer) specifically to prevent state-changing operations from being triggered by cross-origin requests. The plugin either omits this validation entirely or implements it incorrectly.

Root Cause

The root cause is missing or incorrect nonce validation in subscriber-list-empty.php. WordPress plugins that mutate persistent state must confirm that a request originated from an intentional user action within the admin interface. Without this check, any HTTP request delivering the required parameters and cookies is treated as legitimate.

Attack Vector

An attacker hosts a page containing an auto-submitting form or image tag pointing at the vulnerable endpoint on a target WordPress site. When an authenticated administrator visits the page, the browser attaches the administrator's session cookies to the outbound request. The plugin executes the subscriber-list clearing routine and destroys the subscriber data. No credentials, privileges, or authentication bypass on the target site are required from the attacker directly. User interaction from the administrator is required, which limits the attack to social engineering scenarios such as phishing links or malicious advertisements. The vulnerability affects integrity of the subscriber data but does not expose data or enable code execution. Technical details are available in the WordPress Plugin Code Review and the Wordfence Vulnerability Report.

Detection Methods for CVE-2025-9895

Indicators of Compromise

Unexplained emptying of the Notification Bar plugin's subscriber list in the WordPress admin
Web server access logs showing requests to subscriber-list-empty.php with Referer headers from external, untrusted domains
Administrator sessions loading external URLs immediately before the subscriber list is cleared
Absence of expected WordPress nonce parameters (_wpnonce) in requests targeting the plugin endpoint

Detection Strategies

Monitor HTTP access logs for GET or POST requests to the plugin path containing subscriber-list-empty.php
Alert on requests to sensitive plugin endpoints where the Referer header does not match the site's own domain
Correlate WordPress audit logs (via plugins such as WP Activity Log) with web server logs to identify state changes triggered by cross-site requests

Monitoring Recommendations

Enable a WordPress activity logging plugin to record plugin-level administrative actions with timestamps and originating IP addresses
Ingest WordPress and web server logs into a centralized SIEM to correlate administrator browsing activity with destructive plugin actions
Baseline normal traffic patterns to plugin admin endpoints and alert on anomalies outside expected administrative hours

How to Mitigate CVE-2025-9895

Immediate Actions Required

Deactivate the Notification Bar plugin until a patched version becomes available
Restrict administrator browsing habits and require dedicated browser profiles for WordPress administration
Back up the current subscriber list to prevent permanent data loss from a successful CSRF attack
Enforce short session lifetimes for WordPress administrators to reduce the exposure window

Patch Information

At the time of publication, no fixed version is listed in the NVD entry. Administrators should monitor the plugin's WordPress.org repository and the Wordfence Vulnerability Report for an update beyond version 2.2 that adds nonce validation to subscriber-list-empty.php.

Workarounds

Deploy a web application firewall rule that blocks external requests to subscriber-list-empty.php when the Referer header is missing or off-domain
Require administrators to authenticate through a separate browser or private session dedicated to WordPress administration
Apply the principle of least privilege by limiting the number of accounts with administrator-level access to the WordPress site
Consider replacing the plugin with a maintained alternative that implements CSRF protection on all state-changing operations

bash

# Example WAF rule (ModSecurity) to block cross-origin requests to the vulnerable endpoint
SecRule REQUEST_URI "@contains subscriber-list-empty.php" \
  "id:1009895,phase:1,deny,status:403,log,\
  chain,msg:'Block CSRF attempt against Notification Bar plugin (CVE-2025-9895)'"
    SecRule REQUEST_HEADERS:Referer "!@beginsWith https://your-site.example.com" "t:none"