CVE-2023-6941 in Keap Official Opt-in Forms Plugin
Summary
by MITRE • 01/15/2024
The Keap Official Opt-in Forms WordPress plugin through 1.0.11 does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example, in multisite setup).
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Analysis
by VulDB Data Team • 06/20/2025
The CVE-2023-6941 vulnerability affects the Keap Official Opt-in Forms WordPress plugin version 1.0.11 and earlier, presenting a critical security risk through stored cross-site scripting flaws. This vulnerability specifically targets the plugin's handling of user settings where input sanitization and output escaping mechanisms are inadequate, creating a pathway for persistent malicious code execution within the WordPress environment.
The technical flaw stems from the plugin's failure to properly sanitize and escape user-controllable input parameters within its administrative settings. When high-privilege users such as administrators interact with the plugin's configuration interfaces, they can inject malicious script code that gets stored in the WordPress database. This stored content is subsequently served to other users without proper sanitization, enabling attackers to execute arbitrary scripts in the context of the victim's browser session.
The vulnerability's impact is particularly severe in multisite WordPress installations where the unfiltered_html capability is typically restricted for security reasons. Even when WordPress security policies disallow unfiltered HTML content for most user roles, administrators working with this vulnerable plugin can bypass these restrictions through the stored XSS vector. This creates a scenario where privileged users can inject malicious scripts that persist across user sessions and potentially escalate privileges or steal session cookies.
From a cybersecurity perspective, this vulnerability aligns with CWE-79, which describes Cross-Site Scripting flaws where applications fail to properly validate or escape user-controllable data. The ATT&CK framework categorizes this as a code injection technique under the T1566.001 sub-technique for "Phishing with Spoofed Credentials", as attackers can leverage the stored XSS to create convincing malicious content that appears legitimate to end users. The vulnerability also relates to T1213.002 for "Access to Cloud Storage", as compromised administrator sessions could potentially access sensitive data stored within the WordPress environment.
The operational impact extends beyond simple script execution, as successful exploitation could enable attackers to perform actions such as modifying plugin settings, accessing sensitive data, or even compromising entire WordPress installations. In a multisite environment, this vulnerability could allow attackers to affect multiple sites within the network, potentially creating a lateral movement vector for broader attacks. The persistent nature of stored XSS means that once exploited, the malicious code continues to execute until manually removed from the database, making it particularly dangerous for long-term compromise.
Organizations should immediately update to the latest version of the Keap Official Opt-in Forms plugin where this vulnerability has been addressed. System administrators should also implement additional monitoring for suspicious administrative activities and consider implementing Content Security Policy headers to mitigate potential exploitation. Regular security audits of WordPress plugins should include verification of sanitization practices and proper escaping of user input. The vulnerability demonstrates the critical importance of input validation and output escaping in web applications, particularly when dealing with privileged user interfaces where the potential for damage is significantly amplified.