Hackers Exploit Gravity SMTP WordPress Plugin Bug to Expose API Keys
Vulnerability: Attackers exploit Gravity SMTP plugin flaw (CVE-2026-4020) to steal API keys and system data from 100,000+ WordPress sites.
Deep Analysis and Expert Commentary
The vulnerability stems from an improperly secured REST API endpoint (/wp-json/gravitysmtp/v1/tests/mock-data) that unconditionally grants access to unauthenticated users. When triggered with a specific query parameter (?page=gravitysmtp-settings), the endpoint leaks 365 KB of JSON data, including PHP version, database details, active plugins, and third-party API keys (e.g., Amazon SES, Google). Attackers leverage this to impersonate email services or map attack surfaces. The exploit's low complexity (CVSS 5.3) belies its high utility for credential theft and reconnaissance. Mitigation requires immediate plugin updates, credential rotation, and log review for IOC-based detection (e.g., requests from 45.148.10.95). The mass scanning (4M+ daily requests) indicates widespread automation, suggesting attackers are prioritizing low-hanging fruit.
Action Items
- Update Gravity SMTP plugin to version 2.1.5 or later
- Rotate all API keys and OAuth tokens configured in the plugin
- Review server logs for requests to /wp-json/gravitysmtp/v1/tests/mock-data from known malicious IPs
Original Article Brief Intro
The Hacker News · 2026-06-20 · Vulnerability: Attackers exploit Gravity SMTP plugin flaw (CVE-2026-4020) to steal API keys and system data from 100,000+ WordPress sites.
Related Terms and Notes
CVE IDs
- CVE-2026-4020 — Information disclosure flaw in Gravity SMTP plugin exposing API keys and system data via unauthenticated REST API access.
Techniques / TTPs
- Credential_Theft
Context Notes
- API Key Leak
- API_Exposure
- Gravity SMTP
- OAuth tokens — Authentication tokens used to authorize access to third-party services like Google or Amazon SES without sharing passwords.
- WordPress
- WordPress Vulnerability