External Login (<= 1.11.2) — Unauthenticated SQL Injection (CVE-2025-11177): What WordPress Owners Must Do Right Now

Author: Hong Kong Security Expert Team | Date: 2025-10-15

执行摘要

On 15 October 2025 a critical unauthenticated SQL injection vulnerability (CVE-2025-11177) affecting the External Login WordPress plugin (versions ≤ 1.11.2) was publicly disclosed. The bug permits unauthenticated attackers to inject SQL through the plugin’s logging functionality. Consequences range from data disclosure and modification to full site compromise. The issue is rated High (CVSS 9.3) and is exploitable without valid credentials.

This write-up is produced by security practitioners based in Hong Kong with hands-on experience responding to active disclosures. The guidance below is direct, practical and prioritises immediate risk reduction for site owners, administrators and developers.

快速事实

• Vulnerability: Unauthenticated SQL Injection via plugin logging functionality
• Affected plugin: External Login (WordPress plugin)
• Vulnerable versions: ≤ 1.11.2
• CVE: CVE-2025-11177
• Risk level: High (CVSS 9.3)
• 所需权限：无（未经身份验证）
• Public disclosure: 15 October 2025
• Official patch: Not available (as of disclosure)
• Recommended immediate action: Mitigate now — isolate or disable the plugin where possible

这很重要的原因

SQL injection is among the most dangerous web vulnerabilities because it enables attackers to manipulate backend database queries. In WordPress, the database stores user accounts, session tokens, posts, plugin settings, API keys and more. An unauthenticated SQLi means an attacker can begin probing without any login.

This vulnerability stems from the plugin’s logging code: external input intended for logs reaches an SQL context without proper sanitisation or parameterisation. Untrusted data is incorporated into a query, and that allows a range of exploit paths including data theft, privilege escalation and site takeover.

高级技术概述（非利用性）

• The plugin exposes an endpoint that accepts input intended for a plugin-managed logging table or WP option.
• The logging handler constructs an SQL statement with user-supplied data without proper parameterisation or escaping.
• There is no authentication on the endpoint, so remote attackers can send crafted input.
• Result: arbitrary SQL commands can be injected and executed with the WordPress database user’s privileges.

Note: full proof-of-concept exploit strings are deliberately omitted to avoid aiding attackers. This post focuses on protection and response.

Exploitation scenarios

An attacker could use the vulnerability to:

• Read sensitive data: extract hashed passwords, email addresses, API tokens and configuration from wp_users, wp_options and other tables.
• Modify data: change administrator emails, create admin accounts, or alter option values to reference backdoor URLs.
• Drop or corrupt tables, disabling site or plugin functionality.
• Achieve code execution indirectly by changing options that are later executed by vulnerable code.
• Pivot to server-level compromise if database credentials are reused elsewhere.

Because the issue is unauthenticated and web-accessible, automated scanning and exploitation attempts are likely immediately after disclosure. Expect increased noise in server logs.

Detection: what to look for (indicators of exploitation)

If you run External Login (≤1.11.2), proactively search for these indicators:

1. Unusual database queries and slow queries
   • Sudden spike in SQL queries containing embedded SQL keywords in log fields (SELECT, UNION, INTO OUTFILE, –, /*) or excessive comment markers.
   • Check database slow query logs for malformed or abnormally long queries.
2. Anomalous log entries
   • Log rows that include SQL keywords, encoded payloads or long single-column strings that appear like injection attempts.
3. New or modified administrative users
   • Run read-only queries on a copy: SELECT ID, user_login, user_email, user_registered FROM wp_users ORDER BY user_registered DESC LIMIT 10;
   • Look for accounts created outside normal operations.
4. Unexpected option changes
   • Inspect wp_options for edits to siteurl, home, active_plugins and autoloaded options that contain external URLs or base64 strings.
5. Unexpected file changes
   • Check for new PHP files in uploads, wp-content/mu-plugins or theme/plugin directories and any altered timestamps.
6. Webserver logs
   • Requests to plugin endpoints with unusual GET/POST payloads, especially SQL tokens or percent-encoded quotes/comment markers.
7. Outbound network activity
   • Look for unexpected outbound HTTP/S connections to suspicious domains triggered by modified code.

If you observe any of the above, assume possible compromise and proceed to incident response and remediation.

Immediate mitigation — do this right now (prioritised list)

1. Place the site in maintenance/limited access mode

   Limit traffic via hosting controls, .htaccess/NGINX rules or server firewall while assessing.

2. Disable or remove the External Login plugin

   Deactivating and deleting the plugin is the most reliable mitigation until a fixed version is released. If you cannot access wp-admin, rename the plugin directory via SFTP/SSH: wp-content/plugins/external-login -> external-login.disabled.

3. Block plugin endpoints with server rules

   Add .htaccess (Apache) or server-level rules to block requests to known vulnerable plugin files used for logging.

   Example (Apache):

   <Files "external-login-handler.php">
     Require all denied
   </Files>

   Replace external-login-handler.php with the actual filename if known. Prefer disabling the plugin rather than relying on obscurity.

4. Apply request filtering and rate-limiting

   Server-level request filtering or a properly configured WAF can block common SQLi payloads and slow automated probes. Use detection-only mode first to avoid false positives. Note: filtering is an interim control — not a substitute for removing the vulnerable code.

5. Rotate database credentials and secrets if compromise suspected

   If you see evidence of data exfiltration or unauthorized changes, change the DB password and update wp-config.php. Rotation helps only if attackers do not already have file-level access; if files are modified, complete a forensic review first.

6. Audit access logs and isolate suspicious IPs

   Identify and block clearly malicious IPs using hosts.deny, firewall rules or server blocklists.

7. Back up the site now

   Create a full site and database backup (preserve the potentially-compromised state for forensic analysis), and prepare a clean offline copy for restoration if required.

Virtual patching: what request filtering can and cannot do

Request filtering or WAFs can reduce risk by blocking malicious requests before they reach the application, but have limits:

What request filtering can do

• Block common SQL injection payloads and patterns targeting the vulnerable endpoint.
• Rate-limit and geo-block suspicious traffic to slow automated attacks.
• Block known IOCs and exploit signatures and provide logging/alerts.

What request filtering cannot guarantee

• Highly targeted or obfuscated payloads may bypass generic filters.
• If exploitation already occurred, filtering cannot repair modified database entries or backdoored files.
• Logging-based SQLi may accept benign-looking input that later alters SQL structure; simple signature rules can miss this.

In practice, combine endpoint blocking, request filtering and plugin deactivation for the strongest short-term risk reduction.

Recommended generic request-filtering rule examples (sanitised)

Below are generic ModSecurity-style patterns to adapt in your environment. Test in detection-only mode before enforcing.

SecRule REQUEST_URI|ARGS|REQUEST_HEADERS "@rx (?i)(\b(select|union|insert|update|delete|drop|concat|into)\b).*(--|/\*|\#|;)"
    "id:1002001,phase:1,deny,log,msg:'Block probable SQLi payload',severity:2"

SecRule ARGS_NAMES|ARGS "@rx (?i)(\-\-|/\*|\#)"
    "id:1002002,phase:2,deny,log,msg:'Block SQL comment markers in parameters',severity:2"

SecRule ARGS "@validateByteRange 0-4096" "id:1002003,phase:2,pass,log,msg:'Large parameter blocked'"

# Whitelist approach for plugin endpoint (if endpoint is not publicly required)
SecRule REQUEST_URI "@contains /wp-json/external-login/" "phase:1,pass,ctl:ruleEngine=DetectionOnly"
SecRule REMOTE_ADDR "!@ipMatch 192.0.2.0/24 203.0.113.0/24" "phase:1,deny,msg:'Block external access to external-login API'"

Do not deploy aggressive site-wide blocking on database-related terms; this will likely break legitimate functionality. Tune rules carefully.

Safe code-level mitigation (mu-plugin)

If removing the plugin is not possible immediately, create a must-use (mu) plugin that disables the vulnerable logging handler or filters input before it reaches the plugin. A mu-plugin runs earlier and cannot be deactivated via admin, making it useful for emergency overrides.

Example mu-plugin (place as wp-content/mu-plugins/disable-external-login-logging.php):

<?php
/**
 * Emergency mitigation: disable External Login logging handlers
 * Place this file in wp-content/mu-plugins/
 */

add_action( 'plugins_loaded', function() {
    // Attempt to remove the known hook name if the plugin registers it
    // Replace 'external_login_log_event' with the actual hook name if you know it.
    if ( has_action( 'external_login_log_event' ) ) {
        remove_action( 'external_login_log_event', 'external_login_handle_log', 10 );
    }

    // If the plugin uses an object instance:
    if ( class_exists( 'External_Login_Main' ) ) {
        global $external_login;
        if ( isset( $external_login ) && is_object( $external_login ) ) {
            // Attempt to replace the logging method with a safe stub
            if ( method_exists( $external_login, 'write_log' ) ) {
                // Create a safe stub that does nothing
                $external_login->write_log = function() { return true; };
            }
        }
    }
}, 1 );

注意：

• Hook and method names above are placeholders. They must be adjusted to match the plugin implementation.
• Test on staging first. If you cannot safely disable logging via hooks, prefer disabling the plugin entirely.

For hosts and managed providers — network-level mitigations

• Add network-level rules to block requests that appear to write payloads to the plugin’s logging endpoint.
• Globally block payloads with SQL comments and common injection patterns targeting plugin endpoints.
• Notify customers running the plugin with clear instructions to remove or mitigate the plugin until a patch is released.

Recovery and remediation checklist (if you suspect compromise)

1. Isolate the site: restrict incoming connections and suspend services if required.
2. Preserve forensic evidence: take server images, export database dumps and save logs offline.
3. Restore from a known clean backup: only if you can verify the backup predates the compromise.
4. Rotate all credentials: database, SFTP/FTP, control panel, cloud provider keys, and any secrets stored on the site.
5. Reinstall WordPress core, themes and plugins from official sources after cleanup.
6. Scan for web shells and modified PHP files: inspect wp-content, wp-includes, wp-config.php and uploads.
7. Run a database audit: verify wp_options, wp_users and active_plugins for tampering; check serialized values for external URLs or base64 payloads.
8. Notify affected users and stakeholders as required by law and policy.
9. Conduct a full post-mortem to identify the root cause and preventive measures.

Long-term hardening recommendations

• Principle of least privilege for DB user

  Ensure the DB user in wp-config.php has only necessary privileges; avoid granting FILE unless required.

• Keep plugins and themes updated

  Apply updates promptly and monitor multiple trustworthy sources for advisories.

• Use request filtering and behaviour-based protections

  Behavioural inspection reduces exposure to zero-day attacks. Combine filtering with logging and alerting.

• Audit plugins before installing

  Prefer plugins with active maintainers and a history of security responsiveness.

• Implement file integrity monitoring

  Track changes to PHP files and alert on unexpected modifications.

• Follow secure coding practices

  Sanitise, validate and parameterise external input before sending it to SQL queries.

How to safely test whether your site is targeted

• Do not run exploit code on production systems.
• Use a read-only copy of your site in an isolated staging environment for testing.
• Reproduce issues only in safe environments and avoid publicly posting exploit details.

常见问题解答（FAQ）

Q: Is an official patch available?

A: At public disclosure time, no patched release was available. Monitor the plugin page on WordPress.org for updates and apply patches immediately when released.

Q: Can I virtual-patch this in all cases?

A: Virtual patching can reduce risk but is not a guaranteed fix for logging-based SQLi. The most reliable measure is to deactivate the plugin until a proper code fix is published.

Q: Is a host-provided request filter enough?

A: Good filtering can help while you patch. However, the strongest protection combines plugin removal, request filtering, credential rotation and monitoring.

Q: Should I change my DB password right away?

A: If you suspect compromise or see confirmed evidence of extraction, rotate DB and other credentials after preserving forensic snapshots.

Example detection queries (for forensic teams)

Run these queries on a read-only database copy or after making backups:

-- Recently registered users
SELECT ID, user_login, user_email, user_registered
FROM wp_users
ORDER BY user_registered DESC
LIMIT 20;

-- Suspicious autoloaded options
SELECT option_name, option_value, autoload
FROM wp_options
WHERE autoload = 'yes'
ORDER BY LENGTH(option_value) DESC
LIMIT 50;

-- Search for SQL keywords in plugin log table (replace table name if different)
SELECT * FROM wp_external_login_log
WHERE message REGEXP '(SELECT|UNION|INSERT|UPDATE|DELETE|DROP|INTO|--|/\\*)'
LIMIT 200;

Communications guidance (what to tell stakeholders)

• Be transparent with internal teams: explain a high-severity unauthenticated SQLi exists in a plugin the site uses and that immediate action is underway.
• If user data may have been exposed, follow legal and regulatory notification requirements; consult legal counsel if unsure.
• Keep customers updated on remediation progress and advise password resets if exposure is confirmed.

Immediate recommendations (summary)

1. Back up full site & database now and preserve offline copies.
2. Deactivate the External Login plugin (versions ≤ 1.11.2).
3. If you cannot remove it: block the plugin endpoint at server level and apply request-filtering rules in detection mode first.
4. Scan for indicators of compromise (logs, users, options, files).
5. Rotate credentials if compromise is suspected (DB, SFTP, control panel).
6. Monitor for plugin developer updates and apply official patches as soon as available.

If you need assistance

If you require hands-on remediation or a tailored runbook, engage a qualified security consultant or incident response provider. They can produce a staged ruleset, a customised mu-plugin to disable logging safely, and a forensic plan based on your environment.

Final note from Hong Kong security practitioners

Security is about layers and preparation. CVE-2025-11177 is a reminder to prioritise rapid containment for web-facing vulnerabilities: disable vulnerable components, preserve evidence, and coordinate remediation. If you manage multiple sites or host client systems, treat this disclosure as critical and act immediately.