1. Introduction
WordPress Post By Email Enabled allows content managers to publish blog posts by sending emails to a configured address. This feature, while convenient, can be misused if publishing rules are too permissive, allowing unauthorized users to inject content into the website. A successful exploit could lead to defacement, misinformation, or malicious code execution. Confidentiality, integrity and availability may all be affected.
2. Technical Explanation
WordPress core functionality and several plugins enable posting via email. The vulnerability occurs when this feature is active without sufficient restrictions on who can publish content. An attacker could send an email crafted to appear as a legitimate post, bypassing normal authentication checks. There is no specific CVE associated with the general enabling of this feature; risk depends entirely on configuration.
- Root cause: Insufficient restriction on allowed sender addresses or lack of input validation for email content.
- Exploit mechanism: An attacker sends an email to the configured posting address, containing a crafted message that WordPress interprets as a new post. The subject and body of the email are used to populate the post title and content respectively.
- Scope: All WordPress instances with Post By Email enabled, regardless of version, are potentially affected depending on configuration.
3. Detection and Assessment
Confirming if this feature is active requires checking WordPress settings or plugin configurations. Thorough assessment involves reviewing the publishing rules.
- Quick checks: Check the “Writing” settings in the WordPress admin panel for options related to email posting.
- Scanning: Nessus and other vulnerability scanners may flag this as an informational finding if Post By Email is enabled, but rely on configuration detection.
- Logs and evidence: Examine WordPress debug logs (wp-content/debug.log) for any unusual activity related to post creation via email.
php wp option get allow_comments 4. Solution / Remediation Steps
The following steps outline how to secure or disable the Post By Email feature.
4.1 Preparation
- Ensure you have administrator access to the WordPress admin panel. A roll back plan is to restore from backup if issues occur.
- Changes should be made during a scheduled maintenance window, with approval from relevant IT stakeholders.
4.2 Implementation
- Step 1: If Post By Email is not required, disable the core feature by setting `allow_comments` to ‘0’ in the WordPress database using phpMyAdmin or similar tool.
- Step 2: If a plugin enables Post By Email, deactivate and uninstall the plugin through the WordPress admin panel (“Plugins” section).
- Step 3: If you need to keep the feature enabled, restrict allowed sender addresses to only trusted email accounts within the plugin settings or by modifying the `wp_mail` filter.
4.3 Config or Code Example
Before
// In wp-config.php, no specific restrictions are in place.After
// In wp-config.php or a custom plugin:
define( 'ALLOWED_POST_EMAIL_SENDERS', array( '[email protected]', '[email protected]' ) );
add_filter( 'wp_mail_from', function( $email_address ) {
if ( ! in_array( $email_address, ALLOWED_POST_EMAIL_SENDERS ) ) {
return get_option('admin_email'); // Or a default safe address.
}
return $email_address;
});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 – restrict access to the email posting feature to only authorized users.
4.5 Automation (Optional)
# Example Bash script to disable email posting via wp-cli (requires WP-CLI installed).
wp option update allow_comments 0 --path=/var/www/wordpress
echo "Email posting disabled."5. Verification / Validation
Confirm the fix by checking WordPress settings and attempting to post a test email from an unauthorized address.
- Post-fix check: Run `wp option get allow_comments` via WP-CLI; expected output should be ‘0’ if disabled, or confirm restricted sender list is correctly configured.
- Re-test: Attempt to publish a post by sending an email from an address not included in the allowed senders list. Verify that the post is not created.
- Smoke test: Ensure other WordPress functionality (e.g., regular post creation, comment submission) remains operational.
- Monitoring: Monitor WordPress debug logs for failed post attempts via email.
wp option get allow_comments 6. Preventive Measures and Monitoring
Suggest only measures that are relevant to the vulnerability type. Use “for example” to keep advice conditional, not prescriptive.
- Baselines: Update your WordPress security baseline to include a requirement for disabling or restricting Post By Email functionality.
- Pipelines: Integrate SAST tools into your CI/CD pipeline to scan for insecure configurations in WordPress files and plugins.
- Asset and patch process: Regularly review WordPress plugin configurations during routine asset management checks.
7. Risks, Side Effects, and Roll Back
- Risk or side effect 1: Disabling Post By Email may disrupt workflows for users who rely on it.
- Risk or side effect 2: Incorrectly configured sender lists could block legitimate emails.
- Roll back: 1) If disabled, set `allow_comments` to ‘1’ in the database. 2) If a plugin was uninstalled, reinstall it. 3) Restore original configuration files if necessary.
8. References and Resources
- Vendor advisory or bulletin: https://codex.wordpress.org/Post_to_your_blog_using_email