CVE-2024-8740 is a reflected Cross-Site Scripting vulnerability identified in the GetResponse Forms by Optin Cat plugin for WordPress, a tool widely used for creating marketing forms integrated with GetResponse email marketing services. The vulnerability stems from the plugin's use of the WordPress add_query_arg function without proper escaping of URL parameters, which leads to improper neutralization of user-supplied input during web page generation. This flaw allows an unauthenticated attacker to craft malicious URLs containing arbitrary JavaScript code. When a victim clicks such a link, the injected script executes in the context of the vulnerable website, potentially compromising user data or session information. The vulnerability affects all plugin versions up to and including 2.5.6. The CVSS 3.1 base score is 6.1, reflecting a medium severity level, with an attack vector of network (remote), low attack complexity, no privileges required, but requiring user interaction. The scope is changed (S:C), indicating that exploitation could affect resources beyond the vulnerable component. The impact affects confidentiality and integrity but not availability. No patches or official fixes are currently linked, and no known exploits have been reported in the wild. This vulnerability is categorized under CWE-79, which covers improper neutralization of input leading to XSS. The vulnerability is significant because it can be exploited remotely without authentication, relying solely on social engineering to trick users into clicking malicious links, which is a common attack vector in phishing campaigns.

The primary impact of CVE-2024-8740 is on the confidentiality and integrity of users interacting with vulnerable WordPress sites using the GetResponse Forms by Optin Cat plugin. Successful exploitation can lead to session hijacking, theft of sensitive information such as cookies or credentials, unauthorized actions performed on behalf of the user, and redirection to malicious sites. This can damage user trust, lead to data breaches, and potentially facilitate further attacks such as credential theft or malware distribution. While availability is not directly impacted, the reputational damage and potential regulatory consequences from data exposure can be severe. Organizations relying on this plugin for marketing or customer engagement may face increased risk of targeted phishing attacks leveraging the vulnerability. Since the vulnerability requires user interaction, the scale of impact depends on the effectiveness of social engineering. However, given the widespread use of WordPress and marketing plugins, the potential attack surface is large, affecting small businesses to large enterprises globally.

To mitigate CVE-2024-8740, organizations should immediately update the GetResponse Forms by Optin Cat plugin to a version that addresses this vulnerability once available. In the absence of an official patch, administrators should consider temporarily disabling the plugin or removing it if it is not essential. Implementing Web Application Firewall (WAF) rules to detect and block suspicious query parameters and script injection attempts can reduce risk. Site owners should ensure that all user input is properly sanitized and escaped, especially when using functions like add_query_arg. Educating users about the risks of clicking unsolicited links and employing browser security features such as Content Security Policy (CSP) can help mitigate exploitation. Monitoring web server logs for unusual URL patterns and user reports of suspicious behavior can aid early detection. Additionally, integrating security plugins that scan for XSS vulnerabilities and applying strict input validation on custom code can further reduce exposure.