As security researchers based in Hong Kong, we assess and communicate WordPress plugin risks to help site owners and developers respond promptly. On 3 October 2025 a Cross‑Site Request Forgery (CSRF) vulnerability affecting the Notification Bar plugin (versions ≤ 2.2) was published and assigned CVE‑2025‑9895. The issue is rated low severity (CVSS 4.3) but requires immediate attention because CSRF can coerce authenticated users to perform unwanted actions.

Important summary

• Affected software: Notification Bar plugin (Simple Bar) — versions ≤ 2.2
• Vulnerability type: Cross‑Site Request Forgery (CSRF)
• CVE: CVE‑2025‑9895
• Published: 3 Oct 2025
• Patch status: No official fix available at time of publication
• Patch priority for site owners: Low (CVSS 4.3) — but actionable mitigations recommended
• Required privilege (per reports): Unauthenticated (note: see explanation below)

What is CSRF — a quick, practical explanation

Cross‑Site Request Forgery (CSRF) is an attack where an attacker tricks an authenticated user into submitting requests that change state on a target site. For WordPress this commonly involves forcing an administrator or editor to execute actions such as changing plugin settings, creating or modifying content, or toggling features by luring them to a malicious page.

Effective defenses for WordPress endpoints include cryptographic nonces (verified by wp_verify_nonce(), check_admin_referer(), check_ajax_referer(), or REST API permission callbacks) and robust capability checks (current_user_can()). Endpoints that change state must both verify a valid nonce and check user capabilities. A plugin that omits these checks can expose administrative actions to CSRF; in this case Notification Bar’s request handlers permit actions without proper CSRF protections.

How this specific vulnerability behaves (technical overview)

Public reporting indicates the Notification Bar plugin (≤ 2.2) exposes one or more admin/state‑changing actions that:

• Are reachable via predictable endpoints (admin URLs, admin‑ajax.php, or admin‑post handlers).
• Do not enforce WordPress nonces or proper referer/nonce verification.
• May not perform robust capability checks (or perform them inconsistently).

Because of these missing protections, an attacker can craft a web page that—when visited by an authenticated user (for example, an admin)—triggers HTTP requests the site accepts and processes. Consequences vary: changing notification text or visibility, modifying settings, or enabling content that can be used in follow‑on social engineering. Some databases mark the vulnerability “unauthenticated” to indicate the attacker need not log into the target site; CSRF relies on the victim’s session rather than attacker authentication.

Practical risk and exploitability assessment

• Likelihood of exploitation: Low → Moderate. CSRF requires a victim who is authenticated (usually an admin/editor) to visit a malicious page.
• Impact: Low (CVSS 4.3) but depends on what plugin actions are exposed; chained attacks can increase impact.
• Attack complexity: Low for a targeted victim.
• Exploitation vector: Malicious external webpages, emails, embedded iframes/images triggering crafted requests to vulnerable endpoints.

Operational risk varies by deployment. Sites with many administrators, high trust, or transactional content should treat this with greater urgency.

Immediate actions for site owners and administrators (what to do now)

If you run WordPress sites using Notification Bar (simple-bar), take the following immediate steps.

1. Identify installations.
   • In each site admin: Plugins → Installed Plugins. Search for “Notification Bar” or “simple-bar”.
   • For multiple sites, use WP‑CLI, hosting panels, or your management tooling to enumerate installed plugins.
2. Deactivate the plugin if feasible.

   Deactivating removes the attack surface. If the notification bar is non‑critical, deactivate until a fix is available.

3. If you cannot deactivate: apply mitigations.
   • Restrict access to /wp-admin by IP where practical.
   • Block or restrict plugin admin endpoints at the webserver level for non‑trusted sources.
   • Require 2‑factor authentication for admin accounts (note: 2FA reduces credential compromise risk but does not directly prevent CSRF).
4. Force logout and rotate admin credentials if you suspect suspicious activity (Users → All Users → force password resets or use WP‑CLI to expire sessions).
5. Monitor for suspicious changes. Watch for unexpected notification content, altered plugin settings, or anomalous admin log entries.
6. Use available WAF or hosting controls. If your host or a managed service supports WAF rules, request blocking of suspicious admin POSTs to plugin endpoints (guidance below).
7. Apply official plugin update immediately when it becomes available.

Recommended WAF mitigations — sample rules and guidance (virtual patching)

When an official patch is not available, a Web Application Firewall (WAF) can provide temporary protection. Below are high‑level strategies and example configurations. Test carefully before deployment to avoid blocking legitimate admin workflows.

High‑level WAF strategies

• Block or throttle external POSTs to known plugin admin endpoints unless they contain a valid nonce or valid authenticated cookies.
• Challenge or deny requests with external Referer headers invoking admin actions.
• For admin‑ajax.php or admin‑post.php actions, require presence of a nonce parameter or authenticated session cookies.

Example ModSecurity rule (conceptual)

Adapt to your ModSecurity version and test thoroughly. This is a conceptual pattern:

# Block suspicious HTTP POSTs to admin-post.php or admin-ajax.php targeting notification bar actions
SecRule REQUEST_METHOD "POST" "phase:1,pass,id:100001,chain,log,msg:'Block suspicious POST to Notification Bar admin action'"
  SecRule REQUEST_URI "@rx (admin-ajax\.php|admin-post\.php)" "chain"
  SecRule ARGS_NAMES|REQUEST_HEADERS:Cookie "!@contains _wpnonce" "t:none,deny,status:403,log,msg:'Missing WP nonce for admin POST'"

Nonces are dynamic; enforce the presence of a nonce parameter or valid WP authentication cookie rather than matching specific values. Blocking all POSTs without nonces may break legitimate functionality—tune rules for your environment.

Example Nginx location block (deny POSTs from remote referrers)

location ~* /wp-admin/admin-ajax\.php$ {
    if ($request_method = POST) {
        if ($http_referer !~* "yourdomain\.com") {
            return 403;
        }
    }
    # pass to PHP-FPM...
}

Again—test before deployment. Some legitimate admin tools may POST to admin-ajax.php.

If you use a managed WAF or hosting firewall, ask the provider to apply rules blocking nonce‑less POSTs to the plugin’s endpoints and to log such attempts for review.

How to detect if your site was targeted or exploited

Indicators depend on the actions exposed by the plugin. Typical signs include:

• Sudden or unexpected changes to notification content (text, links, scripts).
• Plugin settings altered in the admin without authorized action.
• Admin log entries showing POSTs to admin‑ajax.php or admin‑post.php with external referers or missing nonces.
• Web server access logs showing external POSTs to plugin endpoints immediately before content changes.

Log analysis tips

• Search webserver logs for POSTs to admin endpoints, for example requests containing admin-ajax.php?action=simple_bar_save.
• Look for external Referer headers corresponding to an admin change.
• Inspect WordPress debug logs and any plugin logs for unexpected POST handling.

WP‑CLI checks

# Example: check plugin file modification times
find wp-content/plugins/simple-bar -type f -printf '%T@ %p
' | sort -n

Plugin developer guidance (how to fix the root cause)

If you maintain the plugin, follow this prioritized checklist to remediate CSRF issues and harden the code.

1. Validate nonces on all state‑changing actions.

   Use wp_nonce_field() for forms and check_admin_referer() or wp_verify_nonce() on handlers. For AJAX, use check_ajax_referer().

2. Enforce capability checks.

   Verify the current user has the required capability before performing changes:

   if ( ! current_user_can( 'manage_options' ) ) {
       wp_die( 'Unauthorized', 'Security', array( 'response' => 403 ) );
   }
   

3. Sanitize and validate inputs. Use sanitize_text_field(), esc_url_raw(), intval(), etc., and reject unexpected input types.
4. Avoid exposing unauthenticated endpoints. If an action must be admin‑only, ensure it cannot be called by unauthenticated requests.
5. Use REST API best practices where applicable. Register routes with permission_callback that checks capabilities.
6. Add unit and integration tests. Test that state‑changing endpoints reject requests missing valid nonces or from unauthorized users.

Example code snippets

Add nonce to a settings form and verify in the handler:

<?php wp_nonce_field( 'simple_bar_save_settings', 'simple_bar_nonce' ); ?>

<!-- In the POST handler -->
if ( ! isset( $_POST['simple_bar_nonce'] ) || ! wp_verify_nonce( $_POST['simple_bar_nonce'], 'simple_bar_save_settings' ) ) {
    wp_die( 'Invalid request: nonce check failed', 'Security', array( 'response' => 403 ) );
}
if ( ! current_user_can( 'manage_options' ) ) {
    wp_die( 'Insufficient permissions', 'Security', array( 'response' => 403 ) );
}

For AJAX handlers:

add_action( 'wp_ajax_simple_bar_save', 'simple_bar_save_callback' );
function simple_bar_save_callback() {
    check_ajax_referer( 'simple_bar_ajax', 'nonce' );
    if ( ! current_user_can( 'manage_options' ) ) {
        wp_send_json_error( 'Unauthorized', 403 );
    }
    // Process and save settings...
    wp_send_json_success();
}

Incident response checklist — if you suspect compromise

1. Isolate: Put the site into maintenance mode or restrict admin access to trusted IPs.
2. Preserve evidence: Make full backups (files + DB) and copy server logs; store logs offline for forensics.
3. Scan: Run thorough malware scans and integrity checks.
4. Review: Audit recent admin actions, new users, cron jobs, and uploads.
5. Remediate: Remove or deactivate the vulnerable plugin; rotate credentials.
6. Clean and recover: Reinstall core and plugins from trusted sources and reapply hardening.
7. Monitor: Monitor logs and site behaviour for at least 30 days.
8. Report: Notify stakeholders and your host if you suspect data exposure or persistence.

If you find evidence of lateral movement or persistence (webshells, unauthorized cron jobs), engage a professional incident responder immediately.

How to test whether your site is vulnerable (safe checks)

Do not run exploit code on production. Use staging or cloned environments.

• Review plugin code for missing nonce checks, search for admin_post_* and AJAX hooks lacking wp_verify_nonce() or check_ajax_referer().
• On a staging copy, create a benign HTML page that performs a POST to the suspected endpoint. If the request succeeds and modifies state without a valid nonce, the site is vulnerable.
• Use security scanners on staging environments to flag missing nonce checks.

Long‑term hardening checklist for WordPress sites

1. Keep WordPress core, plugins and themes up to date.
2. Remove unused or abandoned plugins/themes.
3. Enforce least privilege for user roles.
4. Enable 2‑factor authentication for admin accounts.
5. Limit administrative access by IP where feasible.
6. Use a WAF or hosting firewall that supports virtual patching where appropriate.
7. Regularly back up and test restores.
8. Maintain and review access and application logs routinely.
9. Harden WordPress (disable file editing, protect wp-config.php, limit XMLRPC if not needed).
10. Conduct periodic security audits and penetration testing for high‑value sites.

Developer community notes and recommended disclosure etiquette

• If you discovered this issue, follow coordinated disclosure: contact the plugin maintainer privately and allow reasonable time to fix before public disclosure.
• If you maintain plugins, publish a Vulnerability Disclosure Policy (VDP) so researchers know how to report issues.

Detection and SIEM rules (for hosts and advanced users)

If you collect logs centrally, consider these detections:

• Alert on admin POSTs (admin-ajax.php or admin-post.php) with an external Referer header and without a _wpnonce parameter.
• Alert on POSTs to plugin action values (e.g., action=simple_bar_save) from unusual geolocations or automation user agents.
• Correlate admin POSTs with subsequent plugin setting changes to flag possible forced changes.

Example Splunk‑style query:

index=web access_combined method=POST (uri="/wp-admin/admin-ajax.php" OR uri="/wp-admin/admin-post.php") NOT _wpnonce | stats count by clientip, uri, referer, useragent

Closing and summary

CVE‑2025‑9895 (Notification Bar plugin ≤ 2.2 CSRF) is a real vulnerability that should be addressed even though its CVSS score is low. CSRF attacks rely on authenticated victims and are commonly successful in practice because administrators browse the web while logged into admin sessions. Because no official fix existed at the time of publication, take pragmatic defensive measures:

• If possible, deactivate the plugin.
• If not, restrict admin access, enable 2FA, rotate credentials, and monitor logs closely.
• Deploy WAF protections or hosting firewall rules to block nonce‑less POSTs to plugin endpoints while awaiting an official update.
• Developers should add nonce and capability checks on all state‑changing handlers, sanitize inputs, and add tests.

Small flaws are often chained by attackers into larger campaigns; timely mitigation reduces risk.

Quick reference checklist — What to do in the next 24–72 hours

• Identify if Notification Bar (simple-bar) is installed on any sites.
• If possible, deactivate the plugin until fixed.
• If deactivation is not possible, restrict admin access (IP allowlist) and enable 2FA.
• Deploy firewall rules to block unauthenticated or nonce‑less POSTs to plugin endpoints.
• Rotate admin passwords and force resets for all admins.
• Back up the entire site (files + database) and store offsite.
• Monitor logs and unusual admin activity for 30 days.
• Apply official plugin update as soon as it becomes available.