The new vulnerability CVE-2026-4020 in the popular Gravity SMTP plugin is a reminder that even a seemingly “moderate” security flaw can become a significant threat to thousands of websites. The plugin is used on around 100,000 WordPress sites , and Wordfence has already blocked more than 17 million exploit attempts , recording over four million malicious requests in a single day.
This particular case takes on even greater importance for Greece, as a huge percentage of corporate websites, online stores and information portals are based on WordPress and use SMTP services for email management.
What exactly is happening with Gravity SMTP?
The issue is located in the endpoint /wp-json/gravitysmtp/v1/tests/mock-data, which allows any visitor to access sensitive information without any authentication process.
Learn more: Gravity SMTP: Critical vulnerability in 100,000 WordPress sites
With a simple HTTP request, an attacker can gain access to a complete “System Report” of the website. The data at risk is:
- API keys and OAuth tokens
- SMTP credentials
- Information about the web server and PHP
- List of active plugins and versions
- Database details
- Information about the active theme
Essentially, the attacker obtains a complete technical map of the website, significantly reducing the time needed to design more sophisticated attacks.
Vulnerability protection
First step: Immediate upgrade
The most important action is to immediately upgrade Gravity SMTP to version 2.1.5 or later. Versions 2.1.4 and older remain vulnerable.
The longer the update is delayed, the greater the chance that an automated scanning mechanism will detect and exploit the vulnerability. Updating plugins should be a standard practice, not a process that is performed only when a critical vulnerability is made public.
Second step: Renew all credentials
If Gravity SMTP was used to interface with services such as Amazon SES, Google Workspace, Mailjet, Resend, and Zoho Mail, then the credentials should be considered potentially exposed.
See also: ShapedPlugin update system breach infected WordPress sites
Administrators should immediately proceed to:
- Change API keys
- Renewal of OAuth tokens
- Create new SMTP credentials
- Revoking old Secrets
Even if there are no signs of a breach, proactively renewing your access details is the safest option.
Step Three: Check Log Files
Server logs can reveal whether an exploitation attempt has occurred.
Special attention is required for requests containing: /wp-json/gravitysmtp/v1/tests/mock-data?page=gravitysmtp-settings
The presence of repeated requests to this endpoint may be an indication that the website has been targeted by automated vulnerability scanning tools.
Step Four: Install Web Application Firewall
A modern Web Application Firewall (WAF) can act as an additional line of defense. Services like Cloudflare, Wordfence, or other specialized WAF tools can block malicious requests before they reach WordPress.
At the same time, activating IPS and Rate Limiting significantly reduces the effectiveness of mass automated scans.
How to completely secure WordPress
The Gravity SMTP case proves that protecting a WordPress site does not end with installing a security plugin.
Every administrator should implement basic cybersecurity practices:
- Enable multi-factor authentication (MFA)
- Using strong and unique passwords
- Deactivating unused plugins and themes
- Restricting user rights according to the principle of least privilege
- Regular off-server backups
- Continuous updates to WordPress Core, plugins and themes
- Monitoring logs is equally important, as many attacks can be detected early before they develop into a serious security incident.
See also: Everest Forms Pro: Critical vulnerability allows full control of WordPress sites
Why losing the email channel is so dangerous
Leaked SMTP credentials can allow attackers to send emails using the victim's corporate domain. This means a cybercriminal can launch phishing campaigns that appear perfectly legitimate because they come from a trusted infrastructure. The consequences can include:
- Blacklisting of the corporate domain
- Loss of customer trust
- Stop communicating via email
- Financial losses and damage to the company's reputation
The Gravity SMTP incident is yet another reminder that in the WordPress ecosystem, even a seemingly small vulnerability can have huge business implications. Timely upgrades, credential renewal, and a comprehensive security strategy are now essential requirements for any organization that relies on WordPress to maintain its online presence and operations.
