CVE-2026-13156 in MailerSend Plugin
Summary
by MITRE • 07/20/2026
The MailerSend WordPress plugin before 1.0.8 does not perform a nonce check on its configuration-delete action (it verifies the manage_options capability but ignores the nonce), so an attacker can trick a logged-in administrator into visiting a crafted page that wipes the MailerSend WordPress plugin before 1.0.8's SMTP configuration and deactivates the MailerSend WordPress plugin before 1.0.8, breaking the site's email delivery.
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Analysis
by VulDB Data Team • 07/20/2026
The vulnerability in the MailerSend WordPress plugin affects versions prior to 1.0.8 and represents a critical security flaw that exploits the absence of nonce validation in the plugin's configuration-delete action. This weakness allows attackers to manipulate administrators into performing unauthorized actions through social engineering or cross-site scripting techniques, effectively compromising the site's email delivery infrastructure. The vulnerability stems from the plugin's insufficient input validation practices where it only verifies the manage_options capability but fails to implement proper nonce checking mechanisms that are essential for preventing cross-site request forgery attacks.
The technical implementation of this flaw demonstrates a fundamental security oversight in the plugin's access control methodology. While the plugin correctly validates that the requesting user possesses administrative privileges through the manage_options capability check, it completely bypasses the critical nonce verification step that should accompany any privileged action. This omission creates an exploitable condition where an attacker can craft malicious URLs or pages that, when visited by an authenticated administrator, automatically execute the configuration deletion process without proper user consent or additional authentication measures. The absence of nonce validation directly violates established security best practices and represents a failure to implement proper request integrity verification as outlined in the OWASP Top Ten security principles.
The operational impact of this vulnerability extends beyond simple configuration loss, as it fundamentally disrupts the site's email delivery capabilities by wiping the SMTP configuration settings and subsequently deactivating the plugin. This disruption affects all email functionality that relies on the MailerSend plugin for sending notifications, transactional emails, user registration confirmations, password reset requests, and other critical communication channels. The attack vector typically involves tricking administrators into visiting malicious pages through phishing campaigns, compromised website content, or social engineering tactics where the attacker crafts a page containing embedded JavaScript or direct links that automatically submit requests to the vulnerable plugin endpoint.
From a security framework perspective, this vulnerability aligns with CWE-352 Cross-Site Request Forgery (CSRF) and represents a failure in the principle of least privilege execution. The lack of nonce validation constitutes a clear violation of the WordPress Security Hardening guidelines and demonstrates inadequate protection against unauthorized administrative actions. According to ATT&CK framework category T1078 Valid Accounts, this vulnerability enables attackers to leverage legitimate administrator credentials to perform destructive actions without additional authentication barriers. The exploitation process follows typical CSRF attack patterns where the attacker crafts malicious requests that appear legitimate to the WordPress application due to the absence of proper request origin verification mechanisms.
Mitigation strategies for this vulnerability involve immediate plugin updates to version 1.0.8 or later, which address the nonce validation issue by implementing proper request integrity checks. Administrators should also conduct thorough security audits of their WordPress installations to identify other plugins that may exhibit similar CSRF vulnerabilities, particularly those handling sensitive configuration changes. Additional defensive measures include implementing Content Security Policy headers to prevent unauthorized script execution, monitoring for unusual administrative activities in WordPress logs, and ensuring that all users with administrative privileges maintain strong authentication practices including multi-factor authentication. Organizations should also consider implementing web application firewalls that can detect and block CSRF attack patterns targeting known vulnerable plugin endpoints, while regularly updating their security monitoring tools to identify exploitation attempts against known vulnerabilities in third-party components.