CVE-2025-25062 is a medium-severity Cross-site Scripting (XSS) vulnerability identified in Backdrop CMS versions 1.28.0 and 1.29.0, specifically affecting versions prior to 1.28.5 and 1.29.3 respectively. The vulnerability arises due to improper neutralization of input during web page generation when the CKEditor 5 rich text editor module is used. The core issue is that long text content submitted via node or comment forms is not sufficiently isolated, allowing an attacker with the ability to create such content to embed malicious HTML and JavaScript. This malicious payload is executed only when an administrator edits the infected content, not merely viewing it. The attack vector requires the attacker to have limited privileges (permission to create long text content) and necessitates user interaction from an administrator who must actively edit the compromised content. The vulnerability impacts confidentiality and integrity by potentially allowing script execution in the administrator's browser context, which could lead to session hijacking, privilege escalation, or unauthorized actions within the CMS. However, availability is not affected. The vulnerability is mitigated by the requirement of both attacker privileges and administrator interaction, and it only manifests when the CKEditor 5 module is enabled. No known exploits are reported in the wild, and no official patches are linked yet, although updates to versions 1.28.5 and 1.29.3 presumably address the issue.

For European organizations using Backdrop CMS with CKEditor 5 enabled, this vulnerability poses a moderate risk. If exploited, attackers could execute malicious scripts in the context of an administrator's session, potentially leading to unauthorized access or manipulation of sensitive content and administrative functions. This could compromise the confidentiality and integrity of organizational data managed via the CMS. Given that Backdrop CMS is often used by small to medium-sized enterprises, non-profits, and public sector entities for content management, exploitation could disrupt business operations, damage reputations, and lead to data breaches. The requirement for attacker privileges and administrator interaction reduces the likelihood of widespread exploitation but does not eliminate risk, especially in environments with less stringent access controls or where administrators may unknowingly edit malicious content. The vulnerability does not directly impact availability, so denial-of-service is unlikely. However, the potential for privilege escalation or session hijacking could have cascading effects on organizational security posture.

European organizations should implement the following specific mitigations: 1) Immediately upgrade Backdrop CMS installations to versions 1.28.5 or 1.29.3 or later where the vulnerability is fixed. 2) Restrict permissions rigorously to limit who can create or submit long text content, especially from untrusted or external users. 3) Educate administrators to be cautious when editing content submitted by users with lower privileges, particularly content containing rich text or HTML. 4) Temporarily disable the CKEditor 5 module if upgrading is not immediately feasible, or replace it with a safer alternative editor until patched versions are deployed. 5) Implement Content Security Policy (CSP) headers to reduce the impact of potential XSS by restricting script execution sources. 6) Monitor CMS logs for unusual content submissions or administrator editing activities that could indicate exploitation attempts. 7) Conduct regular security audits and penetration testing focused on CMS input validation and user privilege management. These steps go beyond generic advice by focusing on permission management, administrator awareness, and temporary module disabling as practical controls.