CVE-2023-7027 in POST SMTP Mailer Plugin
Summary
by MITRE • 01/03/2024
The POST SMTP Mailer – Email log, Delivery Failure Notifications and Best Mail SMTP for WordPress plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘device’ header in all versions up to, and including, 2.8.7 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 04/11/2026
The CVE-2023-7027 vulnerability affects the POST SMTP Mailer plugin for WordPress, a widely used email delivery solution that manages email logging and delivery notifications. This plugin serves as a critical component in WordPress environments where email functionality is essential for user registration, password recovery, administrative communications, and various other site operations. The vulnerability resides within the plugin's handling of the 'device' header parameter, which is typically used to track client device information during email delivery processes. The flaw exists in versions up to and including 2.8.7, making a substantial portion of WordPress installations potentially vulnerable if they have not updated to the patched version. This represents a significant security concern given the plugin's widespread adoption across WordPress ecosystems.
The technical implementation of this vulnerability stems from inadequate input sanitization and insufficient output escaping mechanisms within the plugin's codebase. When the plugin processes incoming requests containing the 'device' header parameter, it fails to properly sanitize or escape the input data before storing it in the system or rendering it in web pages. This oversight creates a classic stored cross-site scripting condition where malicious payloads can be permanently stored within the plugin's data structures and subsequently executed whenever legitimate users access pages containing the compromised data. The vulnerability is particularly concerning because it operates without requiring authentication, allowing attackers to exploit it remotely without needing valid user credentials or administrative access to the WordPress installation.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform a wide range of malicious activities through the compromised WordPress environment. An attacker could inject malicious scripts that steal cookies, session tokens, or other sensitive information from authenticated users who access pages containing the stored malicious code. The vulnerability also provides a potential entry point for more sophisticated attacks, including phishing campaigns that can redirect users to malicious sites or execute malicious code on victim machines. Additionally, since the plugin handles email delivery and logging functions, attackers could potentially manipulate email content or intercept communications, making this vulnerability particularly dangerous for business-critical WordPress installations. The stored nature of the XSS means that the malicious code persists in the system until manually removed, creating a long-term threat vector.
Mitigation strategies for CVE-2023-7027 should begin with immediate patching of the affected plugin to the latest version that contains the security fix. WordPress administrators should ensure that all instances of the POST SMTP Mailer plugin are updated to versions that address this vulnerability, as the patch typically includes proper input validation and output escaping mechanisms. Network administrators should implement monitoring solutions to detect potential exploitation attempts by watching for unusual patterns in email headers or device information requests. Additional defensive measures include implementing content security policies that restrict script execution, using web application firewalls to filter malicious requests, and conducting thorough security audits of WordPress installations to identify any other potentially vulnerable components. Organizations should also consider implementing regular security assessments and vulnerability scanning procedures to proactively identify similar issues in their WordPress environments. This vulnerability aligns with CWE-79, which describes cross-site scripting flaws, and represents a typical attack vector that falls under the ATT&CK technique T1566 for initial access through malicious email or web content.