CVE-2025-49881 is a Stored Cross-site Scripting (XSS) vulnerability identified in the CyberChimps Responsive Blocks plugin, affecting versions up to 2.0.5. This vulnerability arises from improper neutralization of user input during web page generation, classified under CWE-79. Specifically, the plugin fails to adequately sanitize or encode input that is later rendered on web pages, allowing an attacker to inject malicious scripts that persist in the application. When a victim accesses the affected page, the malicious script executes in their browser context, potentially leading to session hijacking, credential theft, or unauthorized actions performed with the victim's privileges. The CVSS 3.1 base score is 6.5, indicating a medium severity level. The vector string (AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L) shows that the attack can be launched remotely over the network with low attack complexity, requires low privileges (authenticated user), and user interaction (victim must visit the malicious page). The scope is changed, meaning the vulnerability affects resources beyond the vulnerable component. The impact on confidentiality, integrity, and availability is low to moderate. No known exploits are currently reported in the wild, and no official patches have been linked yet. The vulnerability is relevant to websites using the Responsive Blocks plugin by CyberChimps, which is commonly used in WordPress environments to create responsive content blocks.

For European organizations, the impact of this vulnerability depends largely on the extent of CyberChimps Responsive Blocks usage within their web infrastructure. Organizations running WordPress sites with this plugin are at risk of persistent XSS attacks, which can lead to unauthorized access to user sessions, defacement, or injection of malicious content. This can damage brand reputation, lead to data breaches involving user information, and potentially facilitate further attacks such as phishing or malware distribution. Sectors with high reliance on web presence, such as e-commerce, media, and public services, are particularly vulnerable. The requirement for low privileges means that even non-administrative users with accounts on affected sites could exploit this vulnerability, increasing the attack surface. The changed scope indicates that the vulnerability could affect other components or users beyond the immediate plugin context, potentially amplifying the impact. Given the lack of known exploits in the wild, the threat is currently moderate but could escalate if weaponized. Additionally, compliance with GDPR and other data protection regulations in Europe means that exploitation leading to data leakage could result in significant legal and financial consequences.

1. Immediate mitigation includes auditing all WordPress sites for the presence of CyberChimps Responsive Blocks plugin and identifying versions up to 2.0.5. 2. Until an official patch is released, implement Web Application Firewall (WAF) rules specifically targeting typical XSS payload patterns to block malicious input and output. 3. Enforce strict Content Security Policy (CSP) headers to restrict script execution sources and reduce the impact of injected scripts. 4. Limit user privileges to the minimum necessary, especially for contributors or users who can input content into Responsive Blocks. 5. Conduct regular security reviews and input validation checks on all user-generated content fields within the plugin. 6. Monitor web server logs and user activity for unusual behavior indicative of exploitation attempts. 7. Once a patch is available, prioritize immediate update of the plugin across all affected systems. 8. Educate site administrators and content editors about the risks of XSS and safe content practices. 9. Consider disabling or replacing the plugin with alternatives that have a stronger security track record if patching is delayed.