CVE-2022-2187 in Contact Form 7 Captcha Plugin
Summary
by MITRE • 07/17/2022
The Contact Form 7 Captcha WordPress plugin before 0.1.2 does not escape the $_SERVER['REQUEST_URI'] parameter before outputting it back in an attribute, which could lead to Reflected Cross-Site Scripting in old web browsers
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Analysis
by VulDB Data Team • 08/01/2022
The vulnerability identified as CVE-2022-2187 affects the Contact Form 7 Captcha WordPress plugin version 0.1.1 and earlier, representing a critical security flaw that enables reflected cross-site scripting attacks. This issue stems from inadequate input sanitization within the plugin's handling of server request parameters, specifically the $_SERVER['REQUEST_URI'] variable that is processed without proper escaping mechanisms before being rendered in HTML attributes.
The technical flaw manifests when the plugin fails to sanitize the REQUEST_URI parameter obtained from the HTTP server environment variables. This parameter contains the requested URI path and query string from the client's HTTP request, which when improperly handled can be manipulated by attackers to inject malicious script code. The vulnerability is particularly concerning because it affects older web browsers that may not have robust XSS protection mechanisms, making the attack surface broader than typical modern browser environments. The lack of output escaping creates a direct pathway for attackers to inject malicious JavaScript code that executes in the context of the victim's browser session.
The operational impact of this vulnerability is significant as it allows attackers to perform various malicious activities including session hijacking, credential theft, and redirection to malicious websites. When exploited, the reflected XSS could enable attackers to steal user authentication cookies, modify page content, or redirect users to phishing sites that appear legitimate. The vulnerability affects WordPress installations using the Contact Form 7 Captcha plugin, potentially compromising thousands of websites that rely on this popular form handling solution. Attackers could craft malicious URLs that, when clicked by unsuspecting users, would execute their payload in the victim's browser, making this a particularly dangerous vulnerability for web applications that depend on user interaction.
Mitigation strategies for CVE-2022-2187 include immediate upgrade to version 0.1.2 or later of the Contact Form 7 Captcha plugin where the vulnerability has been patched. Administrators should also implement proper input validation and output escaping mechanisms for all server variables before rendering them in HTML attributes. The fix typically involves applying PHP's htmlspecialchars() function or similar escaping mechanisms to sanitize the REQUEST_URI parameter before output. Organizations should conduct thorough security audits of their WordPress installations to identify other potentially vulnerable plugins or themes that might exhibit similar input handling issues. This vulnerability aligns with CWE-79 which specifically addresses Cross-Site Scripting flaws, and follows ATT&CK technique T1566.001 for Phishing through Social Engineering, as the attack vector relies on users clicking maliciously crafted URLs that exploit browser vulnerabilities. Additionally, implementing Content Security Policy headers and regular security monitoring can provide additional defense-in-depth measures against similar reflected XSS vulnerabilities.