CVE-2020-36727 in Newsletter Manager Plugin
Summary
by MITRE • 06/07/2023
The Newsletter Manager plugin for WordPress is vulnerable to insecure deserialization in versions up to, and including, 1.5.1. This is due to unsanitized input from the 'customFieldsDetails' parameter being passed through a deserialization function. This potentially makes it possible for unauthenticated attackers to inject a serialized PHP object.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 04/09/2026
The Newsletter Manager plugin for WordPress presents a critical security vulnerability classified as CVE-2020-36727, affecting all versions up to and including 1.5.1. This vulnerability stems from improper input validation within the plugin's handling of user-supplied data, specifically the 'customFieldsDetails' parameter that is processed through a deserialization function without adequate sanitization measures. The flaw creates a pathway for attackers to exploit the plugin's serialization mechanism and inject malicious PHP objects into the application's execution flow. This type of vulnerability falls under CWE-502, which specifically addresses deserialization of untrusted data, and represents a significant risk to WordPress installations that rely on this plugin for newsletter management functionality. The insecure deserialization vulnerability enables attackers to manipulate the plugin's behavior through crafted serialized objects that can execute arbitrary code when processed by the vulnerable application.
The operational impact of this vulnerability extends beyond simple data manipulation, as it allows unauthenticated attackers to potentially execute malicious code on affected WordPress installations. When the 'customFieldsDetails' parameter is passed through the deserialization function without proper validation, it creates an attack surface where malicious actors can construct serialized PHP objects containing harmful payloads. These payloads can include commands for remote code execution, data exfiltration, or system compromise, depending on the attacker's objectives. The vulnerability is particularly dangerous because it does not require authentication, meaning any user with access to the WordPress site can potentially exploit this weakness. This characteristic aligns with ATT&CK technique T1059.007, which covers the use of PHP for command execution, and represents a significant elevation of privilege threat that can lead to complete system compromise. The vulnerability's exploitation potential is amplified by the fact that WordPress plugins often have elevated privileges and access to sensitive system resources.
Mitigation strategies for CVE-2020-36727 should prioritize immediate plugin updates to versions that address the deserialization flaw, as the vulnerability has been resolved in subsequent releases. Organizations should implement network-level restrictions to limit access to plugin endpoints and consider disabling unnecessary plugin functionality until updates are applied. Input validation and sanitization measures should be enhanced to ensure all user-supplied data undergoes proper validation before processing, particularly for parameters that may be processed through serialization functions. Security monitoring should include detection of suspicious serialized object patterns in plugin request parameters, and regular vulnerability scanning should be implemented to identify similar issues in other installed plugins. The remediation process should also involve reviewing the plugin's code for other potential deserialization vulnerabilities and implementing proper object validation techniques that align with industry best practices for secure coding. Additionally, administrators should consider implementing web application firewalls and application-level controls to prevent exploitation attempts and maintain defense-in-depth strategies against similar vulnerabilities.