CVE-2026-1043 in PostmarkApp Email Integrator Plugin
Summary
by MITRE • 02/19/2026
The PostmarkApp Email Integrator plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin settings in versions up to, and including, 2.4. This is due to insufficient input sanitization and output escaping on the pma_api_key and pma_sender_address parameters. This makes it possible for authenticated attackers, with Administrator-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses the settings page.
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Analysis
by VulDB Data Team • 06/02/2026
The PostmarkApp Email Integrator plugin for WordPress presents a significant security vulnerability classified as stored cross-site scripting that affects versions up to and including 24. This flaw resides within the plugin's administrative settings interface and represents a critical weakness in the platform's input validation and output escaping mechanisms. The vulnerability specifically targets the pma_api_key and pma_sender_address parameters, which are processed without adequate sanitization measures that would normally protect against malicious script injection attempts.
The technical implementation of this vulnerability stems from inadequate parameter validation within the plugin's settings handling code. When administrators configure the plugin settings, the pma_api_key and pma_sender_address fields receive input that is not properly sanitized before being stored in the WordPress database. Additionally, the output escaping mechanisms fail to adequately encode the stored values when rendered back to administrators during subsequent page visits. This combination creates an environment where malicious scripts can be permanently stored and executed whenever the settings page is accessed, making it a persistent threat that can affect multiple users over time.
The operational impact of this vulnerability extends beyond simple script execution as it provides attackers with a persistent foothold within the WordPress environment. An attacker with administrator-level access or higher can inject malicious scripts that execute in the context of other administrators' browsers, potentially leading to complete system compromise. The stored nature of this vulnerability means that the malicious code remains active even after the initial injection, continuously executing each time the affected settings page is loaded. This persistent threat can be leveraged to steal session cookies, perform unauthorized actions, or redirect users to malicious sites, fundamentally undermining the security of the WordPress installation.
This vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws in software applications. The issue also maps to ATT&CK technique T1059.007 for command and scripting interpreter, as attackers can execute arbitrary scripts within the browser context of privileged users. The attack vector requires an authenticated administrator account, making it particularly concerning as it bypasses many traditional perimeter security measures. Organizations should implement immediate mitigation strategies including upgrading to patched versions of the plugin, implementing proper input validation and output escaping measures, and monitoring for suspicious administrative activities that might indicate exploitation attempts.
The remediation approach should focus on comprehensive input sanitization and output escaping across all user-controllable parameters within the plugin's administrative interface. Security patches should ensure that all input values are properly validated against expected formats and that output is appropriately encoded before rendering in web pages. Regular security audits of plugin code should include thorough examination of input/output handling practices to prevent similar vulnerabilities from emerging in the future. Organizations should also consider implementing additional security controls such as role-based access restrictions and monitoring of administrative activities to detect potential exploitation attempts before they can cause significant damage to the WordPress environment.