CVE-2025-27754 is a stored Cross-Site Scripting (XSS) vulnerability identified in the RSBlog! component versions 1.11.6 through 1.14.4 for the Joomla content management system. This vulnerability arises due to improper neutralization of input during web page generation (CWE-79), allowing authenticated users to inject malicious JavaScript code into the plugin's resources. The injected payload is stored persistently by the application and executed in the browsers of other users who view the affected content. The vulnerability has a CVSS 3.1 base score of 6.5, indicating a medium severity level. The vector indicates that the attack can be performed remotely over the network (AV:N) but requires high attack complexity (AC:H), no privileges (PR:N), and no user interaction (UI:N). The scope is changed (S:C), meaning the vulnerability affects components beyond the initially vulnerable component. The impact affects confidentiality, integrity, and availability at a low level. Although exploitation requires an authenticated user, no user interaction is needed for the payload to execute once injected. Stored XSS vulnerabilities can be leveraged to hijack user sessions, deface websites, perform phishing attacks, or deliver malware. Since RSBlog! is a popular blogging extension for Joomla, which is widely used for content management, this vulnerability can affect many websites that use this component without patching. No known exploits in the wild have been reported yet, and no official patches have been linked, indicating that mitigation may require manual updates or configuration changes once available.

For European organizations, the impact of this vulnerability can be significant, especially for those relying on Joomla-based websites with the RSBlog! component installed. Exploitation could lead to unauthorized execution of malicious scripts in the browsers of site visitors, potentially compromising user credentials, session tokens, or delivering further malware. This can damage the organization's reputation, lead to data breaches involving personal data protected under GDPR, and cause service disruptions. Since the vulnerability requires an authenticated user to inject the payload, insider threats or compromised accounts pose a risk. The persistent nature of the stored XSS means that once exploited, multiple users can be affected over time. European organizations in sectors such as e-commerce, media, education, and government that use Joomla for public-facing websites are particularly at risk. Additionally, the cross-site scripting can be used as a stepping stone for more advanced attacks, including privilege escalation or lateral movement within the network if combined with other vulnerabilities.

1. Immediate mitigation involves restricting access to the RSBlog! component to trusted users only and monitoring for suspicious activity from authenticated users. 2. Implement strict input validation and output encoding on all user-supplied data within the RSBlog! component, especially for fields that accept HTML or script content. 3. Apply Content Security Policy (CSP) headers to limit the execution of unauthorized scripts on the website. 4. Regularly update Joomla and all installed extensions, including RSBlog!, as soon as official patches or updates addressing this vulnerability are released by the vendor. 5. Conduct thorough security audits and penetration testing focusing on web application vulnerabilities, including stored XSS. 6. Educate administrators and users about the risks of XSS and the importance of secure authentication practices to prevent account compromise. 7. Consider deploying Web Application Firewalls (WAFs) with rules designed to detect and block XSS payloads targeting Joomla components. 8. Monitor logs for unusual script injections or anomalous user behavior that could indicate exploitation attempts.