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Upgrading struggling vulnerability management programs to Threat Exposure Management, with Host, CISO Al Lindseth formerly from Plains All American Pipeline and PWC - 6 minute podcast
A critical security vulnerability identified as CVE-2025-11833 has been discovered in the Post SMTP WordPress plugin, affecting over 400,000 active installations worldwide. This WordPress plugin vulnerability was first detected on October 11, 2025, and poses a severe threat to website security. The Post SMTP plugin vulnerability allows unauthenticated attackers to exploit a missing capability check and gain full administrative control over WordPress sites. The security flaw affects all versions of the Post SMTP WordPress plugin up to and including version 3.6.0, enabling unauthorized access to logged email data including password reset messages. Attackers can leverage this WordPress vulnerability to reset administrator passwords and completely hijack websites. Security researchers report that over 4,500 attacks exploiting this WordPress plugin vulnerability have already been blocked, highlighting the active threat landscape.
The Post SMTP WordPress plugin, designed to replace the default PHP mail function with an SMTP mailer, contains a critical missing authorization vulnerability tracked as CVE-2025-11833. This WordPress plugin security flaw affects all versions up to and including 3.6.0. The vulnerability stems from a missing capability check in the plugin’s __construct function, which permits unauthorized access to sensitive email log data stored by the WordPress plugin.
An unauthenticated attacker can exploit this WordPress plugin vulnerability to read arbitrary logged emails stored by Post SMTP, including password reset messages and their associated reset links. The attack vector involves triggering a password reset for a WordPress administrator account and then retrieving the corresponding reset email from the plugin’s logs. By accessing this password reset information through the WordPress plugin vulnerability, attackers can change administrator credentials and gain complete administrative control of the WordPress site.
The scope of this WordPress plugin vulnerability extends far beyond individual account compromise, affecting over 400,000 active WordPress installations globally. Once an attacker gains administrative access through this WordPress vulnerability, they can perform any action available to legitimate administrators. This includes uploading and activating malicious plugins or themes, installing backdoors through malicious ZIP files, modifying WordPress posts and pages, and redirecting site visitors to malicious destinations. The WordPress plugin vulnerability therefore enables complete account and site takeover scenarios.
The Post SMTP WordPress plugin vulnerability is classified under CWE-862 (Missing Authorization) and affects the Common Platform Enumeration (CPE): cpe:2.3:a:wordpress:wordpress::::::::. The critical nature of this WordPress vulnerability has earned it a Red threat level designation, indicating the severe risk it poses to WordPress site security and the urgent need for immediate remediation.
Organizations running the Post SMTP WordPress plugin must immediately update to version 3.6.1 or later, which was released on October 29, 2025, and includes proper authorization checks to remediate the vulnerability. After applying the WordPress plugin security patch, administrators should audit all WordPress user accounts and password reset logs for any signs of unauthorized access that may have occurred between initial installation and patching. If the vulnerable WordPress plugin version was publicly accessible, enforce mandatory password resets for all administrative accounts. Additionally, review any site modifications made during the vulnerability window to identify and remove potential malicious changes to the WordPress installation.
Implement Web Application Firewall (WAF) rules specifically designed to block unauthorized access to WordPress REST API endpoints and enhance overall request filtering capabilities. Enable multi-factor authentication (MFA) for all WordPress administrative accounts to significantly reduce the risk of credential-based compromise through this or similar WordPress plugin vulnerabilities. Apply network segmentation strategies to restrict access to WordPress admin interfaces and minimize exposure to external threats targeting WordPress installations.
TA0001 – Initial Access: T1190 (Exploit Public-Facing Application) – Attackers exploit the WordPress plugin vulnerability in publicly accessible Post SMTP installations to gain initial access to WordPress sites.
TA0002 – Execution: T1059 (Command and Scripting Interpreter) – After compromising WordPress admin accounts through the plugin vulnerability, attackers can execute commands and scripts.
TA0003 – Persistence: T1078 (Valid Accounts) – Attackers use compromised WordPress administrator credentials obtained through the vulnerability to maintain persistent access.
TA0004 – Privilege Escalation: T1098 (Account Manipulation) – Attackers manipulate WordPress administrator accounts by resetting passwords through the plugin vulnerability to escalate privileges.
TA0009 – Collection: T1005 (Data from Local System) – Attackers collect email log data from the vulnerable WordPress plugin including password reset information.
TA0009 – Collection: T1114 (Email Collection) – The WordPress plugin vulnerability specifically enables collection of email data stored in Post SMTP logs.
TA0007 – Discovery: T1040 (Network Sniffing) – Attackers may employ network sniffing techniques as part of broader WordPress site reconnaissance activities.
WordPress Plugin Update Information: https://wordpress.org/plugins/post-smtp/#developers
Wordfence Vulnerability Analysis: https://www.wordfence.com/blog/2025/11/400000-wordpress-sites-affected-by-accounttakeover-vulnerability-in-post-smtp-wordpress-plugin/
Detailed Threat Intelligence Report: https://www.wordfence.com/threat-intel/vulnerabilities/wordpress-plugins/post-smtp/postsmtp-complete-smtp-solution-with-logs-alerts-backup-smtp-mobile-app-360-missingauthorization-to-account-takeover-via-unauthenticated-email-log-disclosure
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