Urgent: How the OAuth Single Sign On – SSO (OAuth Client) Plugin CSRF (CVE-2025-10752) Affects Your WordPress Site — and What You Must Do Now

Published: 25 September 2025

Severity: Low (CVSS 4.3)

Vulnerable versions: <= 6.26.12

Fixed in: 6.26.13

CVE: CVE-2025-10752

As a Hong Kong security expert with hands-on experience defending WordPress sites in regional production environments, this guide explains what the CSRF issue in the OAuth Single Sign On – SSO (OAuth Client) plugin means for your site, how attackers could abuse it, and clear, actionable steps you should take immediately.

Executive summary (short)

• The OAuth Single Sign On – SSO (OAuth Client) plugin versions up to and including 6.26.12 are affected by a CSRF vulnerability (CVE-2025-10752).
• An attacker can trigger state-changing plugin actions by tricking a logged-in administrative user into visiting a crafted page.
• Update to version 6.26.13 or later as the primary remediation.
• If you cannot update immediately, apply WAF/virtual-patch protections and follow the incident checklist below.

What exactly is wrong? (technical overview)

Cross-Site Request Forgery (CSRF) occurs when an application performs state-changing operations without verifying that the request was intentionally issued by the authenticated user. WordPress normally uses nonces and same-origin checks to mitigate this.

In this vulnerability certain plugin actions that modify settings or perform privileged changes do not validate CSRF protections (for example, missing or improperly validated nonces and/or referer/origin checks). If an administrative user is logged into the dashboard, an attacker can craft a page that causes the user’s browser to submit requests — authenticated by the user’s session cookie — that invoke plugin behavior on the site.

• Exploitation requires a privileged user (typically an admin) to be authenticated and to visit or load content from an attacker-controlled site.
• The vulnerability is rated Low (CVSS 4.3) largely because it requires social engineering to get a privileged user to load a malicious page and because impact depends on site configuration.
• Fixed in plugin release 6.26.13 — updating is the recommended action.

Realistic attack scenarios

1. Administration change-out:

   An attacker crafts a hidden form or JavaScript request targeting the plugin’s settings action to set malicious redirect URIs, change OAuth client IDs/secrets, or disable security checks. When an admin loads the attacker page while authenticated, the request executes and changes plugin configuration.

2. Account linking / unauthorized session creation:

   If the plugin accepts OAuth callbacks or links external accounts, parameters may be manipulated to link attacker-controlled identities to existing accounts or to alter authentication flows.

3. Privilege escalation via secondary functionality:

   Some endpoints can influence roles or create accounts. A CSRF request could, in specific configurations, alter permissions or create elevated users.

4. Persistence changes and backdoor placement:

   Settings could be changed to enable insecure callbacks, attacker-controlled endpoints, or logging that aids follow-on attacks.

Attackers commonly use phishing, malicious support tickets, or embedded content to lure admins. Because many sites have a small admin set, a single successful lure is sufficient for compromised configuration.

How to check if you are vulnerable (quick checklist)

1. Identify plugin version

   Dashboard → Plugins → find “OAuth Single Sign On – SSO (OAuth Client)”. If version ≤ 6.26.12, you are vulnerable. 6.26.13 or later contains the fix.

2. Confirm exposure vectors

   Does the plugin expose REST endpoints, admin-post.php actions, or admin-ajax calls that alter configuration? These are common places where CSRF protections are required.

3. Search logs for suspicious POST/GET calls

   Look for requests targeting plugin paths or admin endpoints in days around the vulnerability disclosure. Check for unusual referers, user agents, and unexpected source IPs targeting plugin parameters.

4. Check user activity

   Review admin users’ recent activity and last login times. Correlate any unusual admin actions with external requests in logs.

Immediate remediation — what to do now (step-by-step)

Prioritize the actions below. If you manage multiple sites, perform steps 1–3 immediately and schedule deeper audits for your next maintenance window.

1. Update plugin (primary fix — do this now)

   In WordPress admin: Plugins → update OAuth Single Sign On – SSO (OAuth Client) to 6.26.13 or later. Test in staging where possible, but apply the update to production quickly if staging is not available.

2. Apply virtual-patch / WAF rules if you cannot update immediately

   If immediate updating is not possible, deploy strict WAF or edge rules that block exploitation patterns for the plugin’s state-changing endpoints (examples provided below). Test carefully to avoid false positives and breakage.

3. Force re-authentication and rotate keys if you suspect compromise
   • Invalidate all active admin sessions — instruct admins to log out and log back in.
   • Rotate OAuth client secrets, tokens, and any API keys used by the plugin. Reconfigure authoritative OAuth clients where needed.
4. Audit for unauthorized changes (post-check)
   • Review plugin settings and OAuth redirect URIs.
   • Search for unexpected admin-level user accounts or modified roles/capabilities.
   • Check for newly injected code or suspicious files under wp-content/uploads or plugin directories.
5. Monitor and alert

   Enable alerts for administrative setting changes. Increase logging around admin POST/GET payloads for a rolling window if feasible.

6. Communicate and document

   Notify site stakeholders and document actions taken, timestamps, and observations — important for audits and follow-up.

Indicators of Compromise (IoCs) and detection tactics

• Unexpected changes to OAuth redirect URIs, client IDs, or client secrets in plugin settings.
• Unauthorized admin user additions or role changes.
• POST requests to plugin-related endpoints with external referers in server logs.
• Admin activity timestamps correlated with suspicious external requests.
• Suspicious WP cron tasks added after the vulnerable timeframe.

Log sources to inspect:

• Web server access logs (nginx/apache) — watch POSTs to admin endpoints such as admin-post.php and admin-ajax.php.
• WordPress audit logs (if available).
• PHP error logs — plugin changes sometimes surface new warnings.
• Hosting control panel logs for file changes.

Suggested WAF / virtual-patching rules (examples you can adapt)

Below are example ModSecurity-style rules and general strategies to reduce risk until updates can be applied. Adapt and test in staging first — overly broad rules can break legitimate functionality.

1) Block POSTs to admin endpoints without a valid referer/origin

SecRule REQUEST_METHOD "@streq POST" "chain,phase:2,deny,id:100001,log,msg:'Block suspicious POST without referer'
  SecRule REQUEST_URI \"@rx (wp-admin/admin-post.php|wp-admin/admin-ajax.php|/wp-json/.*oauth.*|/wp-content/plugins/.*oauth.*)\"
  SecRule &REQUEST_HEADERS:Referer \"@gt 0\" \"chain\"
  SecRule REQUEST_HEADERS:Referer \"!@rx ^https?://(yourdomain\.com|www\.yourdomain\.com)/\"

Notes: blocking requests lacking a Referer can prevent CSRF but some legitimate clients strip Referer headers — tune for your environment.

2) Enforce presence of WordPress nonces for suspected plugin actions

SecRule REQUEST_URI "@rx /wp-admin/admin-post.php.*(action=oauth|action=sso|plugin_action)" "phase:2,chain,deny,id:100002,log,msg:'Missing nonce on OAuth plugin action'"
  SecRule REQUEST_ARGS "!@contains _wpnonce"

3) Rate-limit suspicious setting-change requests

• Limit POST requests to plugin-setting endpoints per IP and per session.
• If an IP sends multiple POSTs targeting plugin parameters in a short time, block for a cooling period.

4) Block suspicious cross-site POSTs and anomalous content-patterns

• Detect and block repeat patterns of parameter combinations known to be used in exploit attempts.
• Monitor POST sizes and payload structures; sudden anomalies merit temporary blocking and investigation.

5) Targeted signature rules

If reliable parameter patterns from exploit attempts are identified (specific parameter names or combinations), add narrowly scoped rules to block those patterns only.

Sample non-malicious CSRF illustration (safe, educational)

The following sanitized example demonstrates how a malicious page could cause an authenticated admin’s browser to submit a POST. This is educational only.

<!-- Educational-only example: attacker-controlled page sends a POST to the target site -->
<html>
  <body>
    <form id="csrfForm" method="POST" action="https://target-site.example/wp-admin/admin-post.php?action=update_oauth_settings">
      <input type="hidden" name="client_id" value="attacker-client-id">
      <input type="hidden" name="redirect_uri" value="https://attacker.example/cb">
    </form>
    <script>
      // If an admin is logged in to target-site.example and visits this page,
      // the browser will submit the form using the admin session cookie.
      document.getElementById('csrfForm').submit();
    </script>
  </body>
</html>

Fixing this class of issue requires server-side validation of a nonce or CSRF token tied to the user session.

Post-exploitation checks — what to inspect after a suspected incident

1. Export and preserve logs immediately (access logs, audit logs).
2. Check plugin settings: OAuth redirect URIs, client IDs/secrets, and enabled providers.
3. Verify WordPress users: look for new admin/editor users and suspicious role changes.
4. Scan the file system for recently modified files under wp-content and plugin directories; check for PHP files in uploads.
5. Invalidate admin sessions and force re-login for privileged users.
6. Rotate secrets: generate new OAuth client secrets and rotate API keys connected to the instance.
7. Look for outgoing connections or scheduled tasks created by an attacker; escalate to full incident response if you find web shells or persistent backdoors.

Long-term hardening recommendations

• Principle of least privilege: Limit admin accounts and use separate accounts for content editing.
• Reduce attack surface: Remove or disable unused plugins.
• Enforce strong authentication: Use multi-factor authentication (MFA) for privileged users.
• Keep everything updated: Regularly patch WordPress core, themes, and plugins.
• Use activity logging and alerts: Track admin actions and set alerts for configuration changes and new admin accounts.
• Isolate environments: Test updates in staging before production rollout.
• Consider managed edge protections: A properly configured WAF or edge rule set can provide virtual patching while you deploy fixes across multiple sites.

Practical timeline of actions (recommended tempo)

• Within 30 minutes: Check plugin version across sites and update any site that can be updated immediately. If you can’t update, enable WAF protections or virtual patching.
• Within 2 hours: Force logout for privileged users and advise admins to avoid visiting unknown sites while authenticated. Rotate OAuth client secrets if you suspect configuration changes.
• Within 24 hours: Complete updates across all sites; perform a full scan and configuration audit. Implement monitoring rules to detect future changes to OAuth settings.
• Ongoing: Keep logs for at least 90 days where feasible and review permissions and accounts monthly.

Final notes from a Hong Kong security expert

CSRF remains a practical technique for attackers when servers fail to validate intent on state-changing requests. CVE-2025-10752 has an available fix — update to 6.26.13. The best defence is timely patching, reducing privileged user exposure, and applying targeted WAF protections when immediate updates are not possible.

If you operate many sites or lack in-house security expertise, consider engaging experienced incident response or managed security services that can deploy virtual patches and perform triage at scale. Maintain clear documentation of actions taken and preserve evidence for forensic needs.

Resources & references

• CVE-2025-10752
• OAuth Single Sign On – SSO (OAuth Client) plugin — check the plugin changelog for version 6.26.13.
• WordPress developer handbook: Nonces and CSRF protection (for plugin authors).
• Server logs, WP audit logs, and file integrity monitoring — follow standard incident response procedures.