CVE-2021-24870 is a vulnerability identified in the WP Fastest Cache WordPress plugin versions prior to 0.9.5. The issue arises from the lack of Cross-Site Request Forgery (CSRF) protection in the plugin's AJAX action named wpfc_save_cdn_integration. This action is responsible for saving CDN integration settings. Because the plugin does not verify the origin of the request, an attacker can craft a malicious request that, when executed by a logged-in user with high privileges (such as an administrator), causes the plugin to process unauthorized changes. Additionally, the plugin fails to properly sanitize and escape some of the options handled by this action, which introduces a Cross-Site Scripting (XSS) risk. This combination means an attacker can trick a privileged user into executing a request that injects malicious scripts into the plugin’s options, potentially leading to persistent XSS attacks. The vulnerability has a CVSS 3.1 base score of 6.1 (medium severity), with an attack vector of network (remote exploitation), low attack complexity, no privileges required to initiate the attack, but user interaction is necessary (the victim must be logged in and visit a malicious page). The vulnerability impacts confidentiality and integrity by allowing attackers to execute arbitrary scripts in the context of the victim’s browser session, which could lead to session hijacking, privilege escalation, or further compromise of the WordPress site. There are no known public exploits in the wild, and no official patches are linked in the provided data, suggesting that mitigation may require manual updates or configuration changes once available. This vulnerability is categorized under CWE-352 (CSRF) and CWE-79 (XSS).

For European organizations using WordPress sites with the WP Fastest Cache plugin, this vulnerability poses a significant risk, especially for sites managed by multiple users with administrative privileges. Exploitation could lead to unauthorized changes in site configuration, injection of malicious scripts, and potential compromise of user sessions and data confidentiality. This could result in defacement, data leakage, or use of the compromised site as a vector for further attacks such as phishing or malware distribution. Given the widespread use of WordPress across Europe for business, government, and personal websites, the impact could be broad, affecting reputation, compliance with data protection regulations such as GDPR, and operational continuity. The requirement for user interaction and logged-in status somewhat limits the attack scope but does not eliminate risk, particularly in environments where users may be targeted via social engineering or phishing campaigns.

1. Immediate mitigation should include updating the WP Fastest Cache plugin to version 0.9.5 or later once available, as this version addresses the CSRF and sanitization issues. 2. Until an official patch is applied, administrators should restrict access to the plugin’s settings to the minimum necessary number of users and ensure that only trusted users have high privileges. 3. Implement Web Application Firewall (WAF) rules to detect and block suspicious AJAX requests targeting wpfc_save_cdn_integration actions. 4. Employ Content Security Policy (CSP) headers to reduce the impact of potential XSS payloads. 5. Educate privileged users about phishing and social engineering risks to reduce the likelihood of them visiting malicious pages that could trigger the CSRF attack. 6. Regularly audit plugin usage and monitor logs for unusual activity related to AJAX actions. 7. Consider disabling or replacing the WP Fastest Cache plugin if timely patching is not feasible, especially for high-risk or critical websites.