CVE-2024-8726 in MailChimp Forms Plugin
Summary
by MITRE • 11/20/2024
The MailChimp Forms by MailMunch plugin for WordPress is vulnerable to Reflected Cross-Site Scripting due to the use of add_query_arg without appropriate escaping on the URL in all versions up to, and including, 3.2.3. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link.
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Analysis
by VulDB Data Team • 02/24/2025
The vulnerability identified as CVE-2024-8726 affects the MailChimp Forms by MailMunch WordPress plugin, specifically targeting versions up to and including 3.2.3. This represents a critical security flaw that exposes websites to reflected cross-site scripting attacks, potentially compromising user sessions and enabling malicious code execution. The vulnerability stems from improper handling of URL parameters within the plugin's codebase, creating an avenue for attackers to inject malicious scripts that execute in the context of victim browsers. The affected plugin is widely used for creating email subscription forms and marketing automation, making it a prime target for exploitation in targeted attacks against WordPress installations.
The technical root cause of this vulnerability lies in the plugin's implementation of the add_query_arg function without proper HTML escaping of output values. This function is commonly used to manipulate URL query parameters in WordPress environments, but when combined with insufficient sanitization measures, it creates opportunities for attackers to inject malicious payloads. The flaw occurs when user-supplied input is directly incorporated into URL parameters without appropriate encoding or validation, allowing attackers to craft malicious URLs containing script tags that get executed when users navigate to these crafted links. This type of vulnerability maps directly to CWE-79, which describes Cross-Site Scripting flaws, and specifically aligns with the reflected XSS category where malicious scripts are reflected off web servers back to users.
The operational impact of CVE-2024-8726 is significant as it allows unauthenticated attackers to exploit the vulnerability without requiring any privileged access to the target system. Attackers can craft malicious URLs containing XSS payloads that, when clicked by unsuspecting users, execute arbitrary scripts in the victims' browsers. This could enable session hijacking, credential theft, defacement of web pages, or redirection to malicious sites. The vulnerability is particularly dangerous because it requires minimal user interaction beyond clicking a link, making it susceptible to social engineering campaigns. The attack vector typically involves sending malicious links through email, instant messaging, or other communication channels where users might be tricked into clicking the links. This vulnerability aligns with ATT&CK technique T1566, which covers spearphishing and social engineering attacks that leverage web-based exploits.
Mitigation strategies for this vulnerability should prioritize immediate remediation through plugin updates to versions that address the XSS flaw. System administrators should ensure all instances of the MailMunch plugin are updated to the latest stable release that includes proper escaping mechanisms for URL parameters. Additionally, implementing web application firewalls with XSS detection capabilities can provide an additional layer of protection during the update process. Organizations should also conduct thorough security assessments of their WordPress installations to identify any other potentially vulnerable plugins or themes that might exhibit similar patterns of insecure parameter handling. The vulnerability highlights the importance of proper input validation and output escaping in web applications, particularly when dealing with URL parameters and user-supplied content, aligning with security best practices outlined in OWASP Top Ten and other industry security frameworks.