CVE-2026-2987 in Simple Ajax Chat Plugin
Summary
by MITRE • 03/12/2026
The Simple Ajax Chat plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'c' parameter in versions up to, and including, 20260217 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
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Analysis
by VulDB Data Team • 03/17/2026
The Simple Ajax Chat plugin for WordPress represents a widely used communication tool that enables real-time messaging within WordPress environments. This particular vulnerability affects versions up to and including 20260217, creating a significant security risk for WordPress sites that rely on this plugin for user interaction and community engagement. The vulnerability stems from inadequate input validation and output escaping mechanisms within the plugin's codebase, specifically targeting the 'c' parameter that handles chat messages and user communications. The flaw allows attackers to inject malicious scripts that persist in the application's database, making it a stored cross-site scripting vulnerability rather than a reflected one. This characteristic means that the malicious code remains embedded in the system and executes every time affected pages are accessed by users, regardless of whether they are authenticated or not.
The technical implementation of this vulnerability occurs when the plugin fails to properly sanitize user input received through the 'c' parameter, which is typically used for chat message content and other user-generated data. The insufficient input sanitization allows attackers to submit malicious JavaScript code that bypasses the plugin's security measures. Additionally, the lack of proper output escaping means that when the stored content is rendered on web pages, the malicious scripts execute within the context of the victim's browser session. This vulnerability operates at the application layer and can be exploited through standard web request mechanisms without requiring any special privileges or authentication. The attack vector is particularly dangerous because it can be triggered simply by visiting a page that contains the malicious content, making it an ideal candidate for mass distribution through various attack vectors including social engineering, compromised websites, or malicious third-party integrations.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform a wide range of malicious activities including session hijacking, credential theft, data exfiltration, and redirection to malicious websites. When users access pages containing the injected scripts, their browsers execute the malicious code within the context of the vulnerable WordPress site, potentially allowing attackers to steal cookies, modify content, or gain unauthorized access to user accounts. The vulnerability affects all users of the affected plugin versions regardless of their authentication status, making it particularly concerning for public-facing websites where unauthenticated access is common. The stored nature of the vulnerability means that the malicious scripts persist long after the initial injection, creating ongoing security risks that can affect multiple users over extended periods. This type of vulnerability also aligns with attack patterns described in the attack technique matrix, specifically relating to web application exploitation techniques that leverage input validation weaknesses to achieve persistent code execution within user browsers.
The security implications of this vulnerability can be addressed through multiple mitigation strategies that align with industry best practices and standards. Immediate remediation should involve upgrading to the latest version of the Simple Ajax Chat plugin where the vulnerability has been patched and properly sanitized. Organizations should also implement proper input validation and output escaping mechanisms at multiple layers of their web applications, following established security guidelines such as those outlined in the OWASP Top Ten and CWE guidelines. The vulnerability demonstrates the critical importance of proper parameter handling in web applications, particularly when dealing with user-generated content. Additionally, implementing content security policies and regular security assessments can help identify similar vulnerabilities before they can be exploited. The incident highlights the need for continuous monitoring and updating of third-party plugins and themes, as well as the importance of maintaining comprehensive security hygiene practices. Organizations should also consider implementing web application firewalls and intrusion detection systems to help identify and block malicious requests targeting known vulnerable parameters. This vulnerability serves as a reminder of the critical importance of input validation and output escaping in preventing cross-site scripting attacks, which are classified under CWE-79 as one of the most common web application security flaws.