How to remediate – WordPress Debug Mode

1. Introduction

2. Technical Explanation

The vulnerability occurs when WordPress debug mode is active, or if it’s disabled but the /wp-content/debug.log file remains accessible. An attacker can directly request this file from the web server and read its contents. The root cause is insecure file access control. Attackers need only know the path to the log file.

• Root cause: Insecure file permissions on /wp-content/debug.log allow public reading.
• Exploit mechanism: An attacker sends an HTTP request to retrieve /wp-content/debug.log. For example, https://example.com/wp-content/debug.log.
• Scope: WordPress installations on any platform (Linux, Windows, etc.) are affected if debug mode is enabled or the log file exists.

3. Detection and Assessment

You can check for this vulnerability by directly attempting to access the debug log file. A thorough assessment involves reviewing your wp-config.php file and checking file permissions.

• Quick checks: Attempt to access https://yourdomain.com/wp-content/debug.log in a web browser. If the file downloads or displays content, it’s vulnerable.
• Scanning: Nessus plugin ID 16829 can detect this issue. This is an example only; results may vary.
• Logs and evidence: Check your web server access logs for requests to /wp-content/debug.log.

curl -I https://yourdomain.com/wp-content/debug.log

4. Solution / Remediation Steps

4.1 Preparation

• No services need stopping, but be aware that modifying wp-config.php can temporarily disrupt website functionality. A roll back plan is to restore the original wp-config.php file.
• Changes should be approved by a senior administrator or security team member.

4.2 Implementation

1. Step 1: Edit your WordPress configuration file, wp-config.php.
2. Step 2: Add the following lines to disable debugging and logging: define('WP_DEBUG', false);
3. Step 3: Add this line to prevent log creation: define( 'WP_DEBUG_LOG', false);
4. Step 4: Save the wp-config.php file.
5. Step 5: Delete the /wp-content/debug.log file from your server using a secure file manager or SSH.

4.3 Config or Code Example

Before

define('WP_DEBUG', true);

After

define('WP_DEBUG', false); define( 'WP_DEBUG_LOG', false);

4.4 Security Practices Relevant to This Vulnerability

List only practices that directly address this vulnerability type. Use neutral wording and examples instead of fixed advice. For example: least privilege, input validation, safe defaults, secure headers, patch cadence. If a practice does not apply, do not include it.

• Practice 1: Least privilege – Limit file system permissions to only the necessary users and processes.
• Practice 2: Secure Defaults – Ensure debugging features are disabled by default in production environments.

4.5 Automation (Optional)

# Example Bash script to check wp-config.php for WP_DEBUG=true
grep -q "define('WP_DEBUG', true);" /path/to/wp-config.php && echo "Debug mode is enabled" || echo "Debug mode is disabled"

5. Verification / Validation

Confirm the fix by attempting to access the debug log file again and verifying that it’s no longer accessible. Check your wp-config.php file for the correct settings.

• Post-fix check: Attempt to access https://yourdomain.com/wp-content/debug.log in a web browser. You should receive a 404 Not Found error or similar.
• Re-test: Run the quick check from Section 3 again; it should no longer show the debug log file.
• Monitoring: Check web server logs for any attempts to access /wp-content/debug.log. An alert could be set if this path is requested.

curl -I https://yourdomain.com/wp-content/debug.log

6. Preventive Measures and Monitoring

Regularly review your WordPress configuration for debugging settings. Implement a secure baseline that disables debug mode in production.

• Baselines: Update your security baseline to include a requirement to disable WP_DEBUG in production environments.
• Pipelines: Include checks in your deployment pipeline to scan wp-config.php files for sensitive settings like WP_DEBUG=true.
• Asset and patch process: Review WordPress configurations during regular security audits or vulnerability scans.

7. Risks, Side Effects, and Roll Back

• Risk or side effect 1: Incorrectly editing wp-config.php could lead to a white screen of death. Mitigation: Restore from backup immediately.
• Roll back: Replace the modified wp-config.php with your original backup copy.

8. References and Resources

• Vendor advisory or bulletin: https://codex.wordpress.org/Debugging_in_WordPress
• NVD or CVE entry: No specific CVE is associated with this general configuration issue.
• Product or platform documentation relevant to the fix: https://codex.wordpress.org/Debugging_in_WordPress