CVE-2022-42096 is a stored cross-site scripting (XSS) vulnerability identified in Backdrop CMS version 1.23.0. Backdrop CMS is an open-source content management system used for building and maintaining websites. The vulnerability arises from improper sanitization of user-supplied input in the Post content functionality, allowing an attacker to inject malicious scripts that are stored and later executed in the context of other users' browsers when they view the affected content. This type of vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation). The CVSS 3.1 base score is 4.8 (medium severity), with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), requiring high privileges (PR:H), requiring user interaction (UI:R), with a scope change (S:C), and limited confidentiality and integrity impact (C:L/I:L), but no impact on availability (A:N). The vulnerability requires an attacker to have authenticated access with high privileges to inject the malicious payload and relies on user interaction for the malicious script to execute. No known exploits are currently reported in the wild, and no official patches or vendor advisories are linked in the provided data. However, given the nature of stored XSS, successful exploitation could lead to session hijacking, privilege escalation, or defacement within the context of the CMS environment.

For European organizations using Backdrop CMS 1.23.0, this vulnerability poses a risk primarily to the confidentiality and integrity of user sessions and data. Attackers with high-level access could inject malicious scripts that execute when other users view the compromised content, potentially leading to theft of authentication tokens, unauthorized actions performed on behalf of users, or manipulation of displayed content. This could result in reputational damage, data breaches involving personal or sensitive information, and disruption of web services. Given the requirement for high privileges and user interaction, the risk is somewhat mitigated but remains significant in environments where multiple users have elevated access or where social engineering could prompt users to interact with malicious content. European organizations in sectors such as government, education, and media that rely on Backdrop CMS for public-facing websites or intranet portals may be particularly vulnerable. Additionally, compliance with GDPR mandates protection of personal data, and exploitation of this vulnerability could lead to regulatory penalties if personal data is compromised.

1. Immediate mitigation should involve restricting high-privilege user access to the CMS to trusted personnel only, minimizing the risk of malicious content injection. 2. Implement strict input validation and output encoding on all user-supplied content, especially in Post content fields, to neutralize potential XSS payloads. 3. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers accessing the CMS. 4. Monitor CMS logs for unusual activity indicative of attempted or successful injection of scripts. 5. If possible, upgrade to a Backdrop CMS version where this vulnerability is patched; if no patch is available, consider applying custom patches or workarounds that sanitize inputs. 6. Educate users about the risks of interacting with unexpected or suspicious content within the CMS environment to reduce the likelihood of successful exploitation via user interaction. 7. Conduct regular security audits and penetration testing focused on web application vulnerabilities, including XSS, to identify and remediate similar issues proactively.