What is CVE-2026-4020?
The Gravity SMTP plugin for WordPress is vulnerable to Sensitive Information Exposure in all versions up to, and including, 2.1.4. This is due to a REST API endpoint registered at /wp-json/gravitysmtp/v1/tests/mock-data with a permission_callback that unconditionally returns true, allowing any unauthenticated visitor to access it. When the ?page=gravitysmtp-settings query parameter is appended, the plugin's register_connector_data() method populates internal connector data, causing the endpoint to return approximately 365 KB of JSON containing the full System Report. This makes it possible for unauthenticated attackers to retrieve detailed system configuration data including PHP version, loaded extensions, web server version, document root path, database server type and version, WordPress version, all active plugins with versions, active theme, WordPress configuration details, database table names, and any API keys/tokens configured in the plugin.
Affected product
Gravity SMTP WordPress Plugin
Remediation Steps
- Update Gravity SMTP plugin to the patched version immediately
- Review configuration files for exposed API keys and secrets
- Rotate all API keys, OAuth tokens, and sensitive credentials that may have been extracted
- Audit access logs for unauthorized API activity
- Implement access controls to restrict unauthenticated requests to plugin endpoints
References
- https://docs.gravitysmtp.com/gravity-smtp-changelog/
- https://plugins.trac.wordpress.org/browser/gravitysmtp/tags/2.1.4/vendor/gravityforms/gravity-tools/src/Providers/class-config-collection-service-provider.php#L103
- https://plugins.trac.wordpress.org/browser/gravitysmtp/tags/2.1.4/vendor/gravityforms/gravity-tools/src/Providers/class-config-collection-service-provider.php#L86
- https://nvd.nist.gov/vuln/detail/CVE-2026-4020