CVE-2025-51990 is a set of stored Cross-Site Scripting (XSS) vulnerabilities affecting XWiki versions up to and including 17.3.0. The vulnerabilities reside in the Administration interface, specifically within the Presentation section of the Global Preferences panel. An authenticated administrator can inject arbitrary JavaScript payloads into three fields: HTTP Meta Info, Footer Copyright, and Footer Version. These inputs are stored persistently and rendered on public-facing pages without proper output encoding or sanitization. Consequently, any visitor to the affected pages, whether authenticated or not, will have the malicious scripts executed in their browser context automatically upon page load, without requiring any additional user interaction. Exploitation of these vulnerabilities can lead to session hijacking, credential theft, unauthorized actions performed via session riding, and further compromise of the application through client-side attacks. The attack vector requires an attacker to have administrator credentials to inject the payloads, but once injected, the impact extends to all users visiting the affected pages. The lack of proper output encoding in a widely used enterprise wiki platform like XWiki poses a significant risk, especially in shared or internet-facing deployments where administrator credentials might be compromised or stolen. No known exploits are currently reported in the wild, and no official patches or CVSS scores have been published as of the vulnerability disclosure date.

For European organizations, this vulnerability presents a serious risk, particularly for those using XWiki as a collaborative platform accessible over the internet or within large intranets. The ability for an attacker with administrator access to inject persistent XSS payloads means that all users accessing the affected pages could be exposed to client-side attacks, potentially leading to widespread session hijacking and credential theft. This could result in unauthorized access to sensitive corporate information, disruption of business processes, and reputational damage. Organizations in sectors with strict data protection regulations, such as finance, healthcare, and government, face heightened compliance risks under GDPR if personal data is compromised through such attacks. The vulnerability's exploitation could also facilitate lateral movement within networks, enabling attackers to escalate privileges or deploy further malware. The threat is amplified in environments where administrator credentials are weak, reused, or susceptible to phishing, increasing the likelihood of initial compromise.

To mitigate this vulnerability, European organizations should immediately review and restrict administrator access to the XWiki Global Preferences panel, enforcing strong authentication mechanisms such as multi-factor authentication (MFA) to reduce the risk of credential compromise. Administrators should audit the HTTP Meta Info, Footer Copyright, and Footer Version fields for any suspicious or unauthorized content and sanitize or remove any injected scripts. Organizations should implement strict input validation and output encoding controls within their XWiki instances, either by applying vendor patches once available or by deploying web application firewalls (WAFs) with custom rules to detect and block malicious script injections and payloads. Regular monitoring of administrator activities and logs can help detect anomalous behavior indicative of exploitation attempts. Additionally, organizations should educate administrators on secure credential management and phishing awareness to prevent initial access. Where feasible, isolating XWiki instances behind VPNs or restricting access to trusted networks can further reduce exposure. Finally, organizations should stay updated with vendor advisories for official patches and apply them promptly upon release.