CVE-2021-36885 in CFDB7 Plugin
Summary
by MITRE • 12/22/2021
Unauthenticated Stored Cross-Site Scripting (XSS) vulnerability discovered in Contact Form 7 Database Addon – CFDB7 WordPress plugin (versions
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Analysis
by VulDB Data Team • 12/26/2021
The vulnerability CVE-2021-36885 represents a critical unauthenticated stored cross-site scripting flaw within the Contact Form 7 Database Addon plugin for WordPress systems. This vulnerability specifically affects versions of the CFDB7 plugin that fail to properly sanitize user input data before storing it in the database. The flaw allows attackers to inject malicious scripts that persist in the database and execute whenever administrators view the stored form submissions through the plugin's administrative interface. The vulnerability stems from insufficient input validation and output escaping mechanisms within the plugin's data handling processes, creating a persistent security risk that can compromise administrative sessions and potentially lead to full system compromise.
The technical implementation of this vulnerability falls under CWE-79 which describes cross-site scripting flaws where untrusted data is improperly incorporated into web pages without proper sanitization. Attackers can exploit this by crafting malicious payloads in form submissions that contain javascript code or other malicious scripts. These scripts are stored in the database and executed when administrators access the submission records through the CFDB7 plugin interface, making this a stored XSS attack vector. The vulnerability is particularly dangerous because it requires no authentication to exploit and can affect any administrator who views the compromised data, potentially leading to session hijacking, privilege escalation, or data exfiltration. The attack chain typically involves an attacker submitting malicious input through a contact form, which gets stored in the database, and then an administrator viewing that data through the plugin's interface triggers the malicious script execution.
The operational impact of CVE-2021-36885 extends beyond simple script execution as it provides attackers with a persistent foothold within WordPress environments. When administrators view compromised form submissions, their browsers execute the malicious scripts, potentially leading to session cookie theft, redirection to malicious sites, or even remote code execution if the attacker can leverage additional vulnerabilities. The stored nature of this XSS means that the attack can persist long after the initial injection, making detection and remediation more challenging. This vulnerability is particularly concerning in multi-user WordPress environments where administrators frequently review form submissions, as it creates a continuous attack surface. The risk is amplified when administrators have elevated privileges, as successful exploitation could lead to complete system compromise and unauthorized access to sensitive data.
Mitigation strategies for CVE-2021-36885 should focus on immediate plugin updates to versions that address the vulnerability, as the vendor has released patches to resolve the input sanitization issues. Organizations should implement comprehensive input validation measures including the use of Content Security Policy headers to limit script execution, regular monitoring of form submission data for suspicious patterns, and privileged access controls to limit who can view form submissions. Additionally, security teams should conduct thorough vulnerability assessments of WordPress installations to identify other potentially vulnerable plugins and ensure proper output escaping mechanisms are in place. Network-based intrusion detection systems should be configured to monitor for suspicious payload patterns in HTTP traffic, and administrators should be trained to recognize signs of XSS attacks. The implementation of web application firewalls can provide additional protection layers, while regular security audits should verify that all plugins and themes maintain proper sanitization practices to prevent similar vulnerabilities from emerging in the future.