Nazwa wtyczki	FindAll Membership
Rodzaj podatności	Authentication vulnerability
Numer CVE	CVE-2025-13539
Pilność	Wysoki
Data publikacji CVE	2025-11-27
Adres URL źródła	CVE-2025-13539

Urgent: Authentication Bypass in FindAll Membership (<= 1.0.4) — What WordPress Site Owners Need to Do Right Now

Data: 27 Nov, 2025
CVE: CVE-2025-13539
Powaga: Critical / CVSS 9.8 — Broken Authentication

A recently disclosed vulnerability affects the FindAll Membership plugin (versions up to and including 1.0.4). It allows an unauthenticated attacker to bypass intended authentication checks via the plugin’s social-login handling. This can let an attacker perform actions that should be restricted to authenticated or higher-privileged users — including creating or taking over accounts and, in worst cases, escalating privileges to administrative access.

As the team behind WP‑Firewall (a managed WordPress Web Application Firewall and security service), we’re issuing this advisory with concrete mitigation guidance, detection steps, and long‑term hardening recommendations. If you run the FindAll Membership plugin, treat this as a high‑priority incident.

Below you’ll find a practical, actionable guide: what the flaw is, how attackers can abuse it, what to do immediately, and more advanced protections you can apply with a WAF and site hardening.

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Streszczenie (TL;DR)

• Vulnerable: FindAll Membership plugin versions <= 1.0.4
• Fixed version: 1.1 — update as soon as possible.
• Risk: Authentication bypass via the social login endpoint — unauthenticated attackers can impersonate or create accounts and potentially escalate to admin.
• Immediate mitigation: If you cannot update immediately, disable the plugin or block its social-login callback endpoints (see WAF/virtual patch rules below).
• Recommended long-term: Update to 1.1, enable WAF virtual patching, audit user accounts and logs, rotate credentials, and add multi-factor authentication for all admin accounts.

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What the vulnerability is (high level)

The FindAll Membership plugin integrates social login functionality to allow users to sign in via third‑party OAuth/OIDC providers. The vulnerability arises from insufficient verification and validation of the social login response and associated parameters during the callback flow. Attackers can craft requests that forge or manipulate the social login exchange to bypass authentication checks and have the plugin treat an unauthenticated request as a valid authenticated user.

Typical root causes in similar social sign‑in vulnerabilities include:

• Missing or improperly validated OAuth/OIDC state parameter and CSRF nonce checks.
• Acceptance of user identifiers or profile data from unverified request parameters instead of validating tokens with the identity provider.
• Logic that creates or maps local WordPress users based on provided fields without server‑side verification.
• Failure to validate access token / ID token signatures or expiry before provisioning the session.

Because code paths rely on those unchecked parameters to create sessions or map user roles, an attacker can supply crafted parameters and trigger an authenticated session, or cause the plugin to create an account with elevated privilege.

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Why this is particularly dangerous

• Authentication bypass means the attacker is not limited to brute‑forcing credentials. They can achieve access without any valid password.
• If account provisioning logic assigns roles automatically (e.g., vendor, moderator), attackers may obtain higher access than a normal user.
• Social login endpoints are typically reachable from the public internet and designed to receive redirected traffic — making them easier to target.
• Exploitation can be automated and scaled, enabling mass account creation or takeover in minutes if left unprotected.

Because of these factors, this vulnerability has a high likelihood of being actively exploited once public details are available. Treat it as a high‑priority remediation.

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Immediate steps you must take (within hours)

1. Patch the plugin to version 1.1 immediately if possible. This is the only guaranteed fix to remove the insecure code paths.
2. If patching is not immediately feasible, temporarily deactivate the plugin until you can update. Deactivating will stop the vulnerable flow.
3. If you must keep the plugin active for business reasons, block the plugin’s social login callback endpoints at the WAF level (see example rules below). This provides an effective virtual patch.
4. Force a password reset and review all recently created accounts and recent login events — look for newly created admin or elevated accounts. Remove or demote unknown users.
5. Rotate credentials and API keys for site administrators and any third‑party services integrated with the site.
6. Enable multi‑factor authentication (MFA) for all admin users immediately.

If you use WP‑Firewall, enabling our managed ruleset and virtual patching will provide an immediate blockade against exploitation patterns for this vulnerability (see the WP‑Firewall plan details and signup link near the end of this article).

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Detection: how to find signs of exploitation

Check logs (web server, WordPress, plugin logs, and WAF logs) for the following indicators of compromise (IoCs) or suspicious activity:

• POST or GET requests to plugin social login callback URLs (look for path fragments such as /wp-content/plugins/findall-membership/ or endpoints containing social, auth, callback, oauth, openiditp.).
• Requests to callback endpoints with suspicious or missing state parameters, e.g., empty or unusually short values.
• High volume of requests with unusual user agent or from unusual IP ranges to social login endpoints.
• Unexpected new user creation timestamps that coincide with suspicious callback activity.
• New users with email addresses from disposable or uncommon domains.
• Sudden account role changes or new admin users created non‑interactively.
• Login events where a user session is created without a prior interactive login flow (track session creation vs. typical login flow).

If you detect any of the above, isolate the site (take offline if necessary), take backups, and follow the incident response checklist below.

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Forensic checklist (what to inspect and export)

• Export webserver logs (access & error logs) for the last 30 days (or since the plugin was installed/updated).
• Export WordPress użytkownicy wp, wp_usermeta, I opcje_wp tables for investigation. Look for unfamiliar admin users, modified capabilities, or suspicious entries.
• Capture the plugin directory and any modified files in wp-content/plugins/findall-membership/.
• Check for persistent backdoors: unknown PHP files in wp-content/przesyłanie, unusual cron tasks (wp_cron), or scheduled events.
• Hash and snapshot the site files for baseline comparison.
• Export WAF logs and review blocked requests for any evidence of exploitation attempts.

Document findings and maintain chain of custody if this is to be investigated further.

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Short-term mitigation via WAF / virtual patching

If you cannot immediately update, use your WAF to apply a virtual patch. Below are conceptual rules and example snippets you can adapt. Do not directly publish exploit parameters — these rules focus on blocking suspicious flows rather than exposing the exploit.

Ważny: test rules on a staging environment before applying to production to avoid false positives.

Example 1 — Block unauthenticated access to social-login callback path (NGINX rewrite / deny):

# NGINX snippet — deny access to known vulnerable callback endpoints
location ~* /wp-content/plugins/findall-membership/.*/(social|auth|callback|oauth|openid) {
    return 403;
}

Example 2 — Apache/mod_security rule (logical sample):

# mod_security rule to block requests missing expected OAuth state or token validation
SecRule REQUEST_URI "@rx /wp-content/plugins/findall-membership/.*(social|callback|auth)" 
    "phase:1,deny,log,status:403,msg:'Blocked FindAll membership social-login callback (virtual patch) - missing valid state/token'"

Example 3 — WAF custom rule (pseudo‑DSL for managed WAFs)

• Block requests to plugin social-login endpoints where:
  • request method is GET or POST to /.../findall-membership/*(social|callback|auth) AND
  • state parameter is missing OR id_token Lub access_token parameter present in query string (instead of in-server-validated flow).
• Rate-limit any IP making > 5 requests to those endpoints in a minute and block for 1 hour.

Example 4 — WordPress level hardening (quick temporary code block)

Place a small mu‑plugin (must‑use plugin) that rejects callback requests until your plugin is updated. Example (drop into wp-content/mu-plugins/disable-findall-callback.php):

<?php
/*
Plugin Name: Temporary block for FindAll Membership social callback
Description: Blocks public access to the plugin social login callback endpoints until patched.
Author: WP-Firewall
*/

add_action('init', function() {
    $uri = $_SERVER['REQUEST_URI'] ?? '';
    if (strpos($uri, '/wp-content/plugins/findall-membership/') !== false &&
        (strpos($uri, 'social') !== false || strpos($uri, 'callback') !== false || strpos($uri, 'auth') !== false)) {
        // Return a 403 for safety
        status_header(403);
        exit('Access blocked for security reasons. Please update the FindAll Membership plugin.');
    }
});

Notatka: This mu-plugin is a blunt instrument intended as a temporary emergency measure. It blocks the social login functionality completely until you can apply the proper patch.

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Permanent remediation (developer guidance / plugin fix)

The only full fix is to update the plugin to the patched release (1.1). If you maintain custom code or want to understand the developer-side mitigations, engineers should:

1. Enforce strict state parameter generation and verification:
   • Generate a unique cryptographically secure state per login attempt and store it server‑side (e.g., $_SESSION or transient) prior to redirecting to the provider.
   • Verify the returned state matches the stored value and is not reused.
2. Validate provider tokens server-side:
   • Exchange authorization codes server-side with the provider’s token endpoint.
   • Validate ID token signatures (for OIDC) or validate access tokens by calling the provider’s token introspection endpoint or userinfo endpoint.
   • Check token expiry and audience (aud) claims.
3. Do not trust provider-supplied profile parameters sent directly in query or POST parameters:
   • Always use the provider API to get canonical user attributes.
   • Map provider user IDs to local user accounts only after token validation.
4. Account creation and role assignment safety:
   • Default to the lowest privilege role for newly created users (e.g., Subscriber).
   • Require verification steps (email verification, step-up authentication) before granting elevated roles.
   • Avoid any auto‑promotion path that grants admin/moderator rights without manual admin approval.
5. Protect callback endpoints:
   • Only accept requests with known referer or origin headers where appropriate and when consistent with OAuth flows.
   • Use POST-only where possible for sensitive callbacks and validate CSRF tokens.
6. Logging & audit:
   • Add robust logging for all social login attempts, including token validation results and any failed checks.

If you are the plugin developer, follow standard secure OAuth integration patterns and consult the provider’s recommended SDKs. If you are a site owner relying on a vendor plugin, update to 1.1 — do not attempt to patch complex auth logic yourself unless you are a professional developer.

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Post‑incident steps (after remediation)

1. Update plugin to 1.1 and confirm the fix is in place.
2. Reset passwords for all admin and privileged users and rotate API keys used on the site.
3. Remove any suspicious accounts or demote them to the lowest role if unsure. Consider full removal of accounts that were clearly malicious.
4. Run a full malware scan (files & database) and perform remediation of any backdoors found.
5. Restore site from a backup if you have evidence of sustained compromise that is difficult to clean. Prefer a pre‑incident clean backup.
6. Review logs for post‑remediation suspicious activity to ensure attackers aren’t persisting access.
7. Conduct an internal review to determine cause, time-to-detect, and missed controls; improve processes accordingly.

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Longer‑term hardening recommendations (reduce future risk)

• Keep WordPress core, themes, and plugins updated. Set up a scheduled update policy and use a test/staging rollout before production.
• Use managed WAF / virtual patching to block exploit patterns for publicly disclosed issues while you deploy code fixes. Virtual patching buys time and reduces exploit risk.
• Enforce multi‑factor authentication for any user with elevated privileges.
• Enforce least privilege: avoid giving plugin/service accounts more capability than needed.
• Limit plugin usage: use only necessary plugins and delete plugins you are not using.
• Protect WP admin by restricting access by IP (where possible), and consider renaming or moving login endpoints to reduce generic attack surface.
• Implement centralized logging and monitoring (including failed login attempts, new user creations, and file modifications).
• Use secure development practices: peer review of code that touches authentication flows and third‑party integrations.

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Sample WAF signatures & detection patterns to monitor

• Monitor requests where URI matches: /wp-content/plugins/findall-membership/ and query strings include state, access_token, id_token, oauth but the token validation endpoints are not called (indirect detection through WAF logs).
• Detect POST requests to callback endpoints with missing or invalid Referer/Origin.
• Flag requests that create sessions without prior normalized login flows (correlate site session creations with login redirect records).

A practical approach: configure alerts for any of the following within a 1‑hour window:

• > 5 requests per minute to social-login endpoints from a single IP.
• > 10 new user registrations from the same IP in an hour.
• New administrator role assignments within a short window post-social-login callback events.

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Incident Response Checklist (concise)

• Apply plugin update (1.1) or deactivate plugin.
• If not updating immediately: apply WAF block rules to social-login endpoints.
• Force admin password resets, enable MFA.
• Audit and remove/demote suspicious accounts.
• Backup logs and site files for forensic analysis.
• Run malware/compromise scan and clean up any findings.
• Rotate credentials and third‑party API keys.
• Review and harden OAuth implementation and plugin usage.
• Inform stakeholders and prepare public communications if compromise occurred.

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Często zadawane pytania

Q: Can I rely solely on a WAF to protect me?
A: A WAF (virtual patch) is a valuable protective layer and can prevent exploitation while you update. However, it is not a substitute for the code fix. Update the plugin as soon as possible and use the WAF as a stopgap.

Q: How long should I keep the virtual patch in place?
A: Keep the WAF rule until you have updated the plugin and fully validated the fix on your production environment. Remove the rule once you are certain the endpoint is secure to avoid long‑term maintenance overhead.

Q: What if my site shows evidence of compromise?
A: Isolate the site where feasible, gather forensic artifacts (logs, DB export, file snapshots), and follow the incident response checklist above. Consider reinstallation from clean backups if the compromise is deep.

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About WP‑Firewall protections (how we help)

At WP‑Firewall we provide managed WAF protection specifically tuned for WordPress ecosystems. For incidents like this FindAll Membership social login bypass, our managed rules include:

• Virtual patches that block common exploit vectors for known vulnerabilities.
• OWASP Top 10 mitigation rules, including protections for broken authentication and session management attacks.
• Malware scanning and remediation tools that find and remove web shells and injected code patterns.
• Behavioral anomaly detection — for example, unusual account-creations and callback-pattern anomalies — with configurable alerting and automated mitigation steps.
• Dedicated support options for vulnerable plugin auto-updates and site remediation (see plan tiers below).

If you already run WP‑Firewall, enable the managed ruleset and ensure virtual patching is active — it will block known exploitation patterns for this vulnerability while you schedule the plugin update.

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Secure your site now — WP‑Firewall Basic is free

Start protecting your WordPress site immediately with WP‑Firewall Basic (Free). The Basic plan includes essential protections that are highly relevant to this vulnerability: a managed firewall, unlimited bandwidth for WAF operations, malware scanning, and out‑of‑the‑box mitigation for OWASP Top 10 risks. These measures are designed to reduce your window of exposure until you can fully patch. Upgrade paths are available if you need automated malware removal, user‑level IP lists, monthly security reporting, or auto virtual patching.

Learn more and sign up here: https://my.wp-firewall.com/buy/wp-firewall-free-plan/

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Final notes — actionable priorities for site owners

1. Update FindAll Membership to 1.1 immediately.
2. If you cannot update immediately, deactivate the plugin or apply WAF rules to block the social login callback endpoints.
3. Audit accounts and reset/rotate credentials and API keys. Enable MFA for admins.
4. Use managed virtual patching where available to minimize exposure while you remediate.
5. Review your WordPress security posture and harden authentication flows, especially for any third‑party integrations.

If you need hands‑on assistance, WP‑Firewall offers services to deploy emergency virtual patches, scan and clean sites, and guide incident recovery. We’re available to help you prioritize and restore secure operations quickly.

Stay safe — treat authentication vulnerabilities with urgency.