CVE-2023-33328 in MailChimp Subscribe Forms Plugin
Summary
by MITRE • 05/28/2023
Auth. (admin+) Stored Cross-Site Scripting (XSS) vulnerability in PluginOps MailChimp Subscribe Form plugin
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Analysis
by VulDB Data Team • 06/17/2023
The CVE-2023-33328 vulnerability represents a stored cross-site scripting flaw within the PluginOps MailChimp Subscribe Form WordPress plugin that affects users with administrator privileges or higher. This vulnerability stems from inadequate input validation and output sanitization mechanisms within the plugin's codebase, specifically when processing user-submitted data through the subscription form functionality. The flaw allows authenticated attackers with admin-level permissions to inject malicious JavaScript code that persists in the application's database and executes whenever the affected page is loaded by other users. This stored nature of the vulnerability makes it particularly dangerous as the malicious payload remains active until manually removed from the database, potentially affecting all users who interact with the compromised form functionality.
The technical implementation of this vulnerability involves the plugin's failure to properly sanitize user input before storing it in the database and subsequently rendering it on web pages without adequate escaping mechanisms. When administrators or privileged users submit form data through the MailChimp subscription interface, the plugin processes this information without sufficient validation to prevent the injection of malicious scripts. The vulnerability manifests when the stored data is later retrieved and displayed in web interfaces, particularly in administrative panels or front-end form displays where the malicious JavaScript code executes in the context of other users' browsers. This creates a persistent threat vector that can be exploited to steal session cookies, redirect users to malicious sites, or perform unauthorized actions on behalf of victims.
The operational impact of this vulnerability extends beyond simple script execution as it provides attackers with elevated privileges within the WordPress environment. An attacker with admin-level access can leverage this vulnerability to establish persistent backdoors, modify plugin configurations, access sensitive user data, or manipulate the subscription form to capture additional credentials. The stored nature of the XSS payload means that the attack can persist even after the initial exploitation, potentially allowing for extended reconnaissance and data exfiltration activities. This vulnerability directly impacts the integrity and confidentiality of the WordPress site's data and can be used as a foothold for further attacks within the broader network infrastructure.
Security mitigations for CVE-2023-33328 should prioritize immediate plugin updates to versions that address the identified sanitization flaws and implement comprehensive input validation measures. Organizations should also deploy web application firewalls that can detect and block suspicious script patterns in form submissions, while implementing strict content security policies to prevent execution of unauthorized scripts. Regular security audits of WordPress plugins should include verification of input sanitization practices and output escaping mechanisms, with particular attention to administrative interfaces where privileged users interact with form data. The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws, and follows ATT&CK technique T1548.001 for privilege escalation through application vulnerabilities. Additionally, implementing principle of least privilege access controls and regular monitoring of administrative form submissions can help detect anomalous activity that might indicate exploitation attempts.