CVE-2018-20988 in wpgform Plugin
Summary
by MITRE
The wpgform plugin before 0.94 for WordPress has eval injection in the CAPTCHA calculation.
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Analysis
by VulDB Data Team • 12/01/2023
The vulnerability identified as CVE-2018-20988 affects the wpgform plugin version 0.93 and earlier in the WordPress ecosystem, presenting a critical security risk through improper input validation and sanitization. This flaw exists within the plugin's CAPTCHA calculation mechanism where user-supplied data is directly passed to the eval() function without adequate sanitization or validation. The issue stems from the plugin's failure to properly escape or filter user inputs before executing dynamic code, creating a path for malicious actors to inject arbitrary code into the WordPress environment.
The technical implementation of this vulnerability follows the pattern of code injection attacks where the eval() function processes user-provided mathematical expressions used in CAPTCHA calculations. When users interact with forms utilizing this plugin, their input is processed through a function that constructs and executes code dynamically. The absence of proper input validation allows attackers to submit malicious payloads that bypass normal execution flows and execute unintended commands on the server. This represents a direct violation of secure coding principles and falls under the CWE-94 category of "Improper Control of Generation of Code ('Code Injection')" which is classified as a critical weakness in software security.
The operational impact of this vulnerability is severe as it provides attackers with arbitrary code execution capabilities on vulnerable WordPress installations. An attacker could leverage this flaw to execute malicious code, potentially leading to full system compromise, data exfiltration, or the installation of backdoors. The vulnerability affects the integrity and availability of the WordPress platform, as compromised installations can be used for various malicious activities including hosting malware, conducting further attacks, or establishing persistent access. The attack surface is broad since the vulnerability is present in the CAPTCHA calculation functionality that is typically used in contact forms, comment systems, and other user interaction points.
Mitigation strategies for this vulnerability include immediate patching of the wpgform plugin to version 0.94 or later where the eval injection issue has been resolved. Administrators should also implement input validation and sanitization measures to prevent similar issues in other components of their WordPress installations. The solution requires replacing dynamic code execution with safer alternatives such as mathematical expression parsers or proper validation libraries. Additionally, implementing web application firewalls and monitoring for suspicious code execution patterns can provide additional defense layers. This vulnerability highlights the importance of following secure coding practices and adheres to ATT&CK technique T1059.007 for "Command and Scripting Interpreter: PowerShell" and T1059.006 for "Command and Scripting Interpreter: Python" in cases where similar injection flaws are present in different contexts, emphasizing the need for comprehensive input validation across all dynamic code execution points.