CVE-2022-42094 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 to build and manage websites. The vulnerability arises from improper sanitization of user-supplied input within the 'Card' content feature, allowing an attacker to inject malicious scripts that are persistently stored and executed in the context of users viewing the affected content. This stored XSS flaw can lead to the execution of arbitrary JavaScript code in the browsers of authenticated users who interact with the compromised content. 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), user interaction (UI:R), scope changed (S:C), and low impact on confidentiality and integrity (C:L/I:L) but no impact on availability (A:N). The requirement for high privileges and user interaction reduces the ease of exploitation, and no known exploits have been reported in the wild. However, the vulnerability still poses a risk to the confidentiality and integrity of user sessions and data within Backdrop CMS installations. The CWE-79 classification confirms this as a classic XSS issue, which can be leveraged for session hijacking, defacement, or delivering further attacks such as phishing or malware distribution within the trusted domain. No official patches or vendor advisories are linked, indicating that mitigation may rely on manual code review or configuration changes until an official fix is released.

For European organizations using Backdrop CMS 1.23.0, this vulnerability could lead to unauthorized script execution within the context of authenticated users, potentially compromising session tokens, user credentials, or sensitive data displayed on the site. This could facilitate targeted phishing attacks, unauthorized actions performed on behalf of users, or defacement of web content, undermining trust and brand reputation. Organizations in sectors such as government, finance, healthcare, and e-commerce, which often rely on CMS platforms for public-facing and internal portals, may face increased risks of data leakage or operational disruption. The requirement for high privileges to exploit the vulnerability limits the attack surface primarily to insiders or compromised accounts, but social engineering or privilege escalation could broaden this. The scope change in the CVSS vector indicates that the vulnerability affects resources beyond the initially vulnerable component, potentially impacting multiple users or subsystems. Given the lack of known exploits, the immediate risk is moderate, but unpatched systems remain vulnerable to future exploitation attempts. European organizations with compliance obligations under GDPR must consider the potential for personal data exposure and the associated regulatory consequences.

1. Immediate mitigation should include restricting access to the 'Card' content editing features to only trusted and necessary personnel to minimize the risk of malicious input. 2. Implement strict input validation and output encoding on all user-supplied content within the CMS, especially in the 'Card' content fields, to neutralize potential script injections. 3. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers accessing the CMS. 4. Monitor user activity logs for unusual behavior indicative of attempted exploitation, such as unexpected script injections or privilege escalations. 5. Conduct a thorough code audit of the Backdrop CMS installation to identify and remediate similar XSS vulnerabilities in other components. 6. Engage with the Backdrop CMS community or maintainers to obtain or contribute patches addressing this vulnerability. 7. Educate CMS administrators and content editors about the risks of XSS and safe content handling practices. 8. Where feasible, isolate the CMS environment or deploy web application firewalls (WAFs) with rules targeting XSS attack patterns to provide an additional layer of defense.