CVE-2025-64672 is a cross-site scripting (XSS) vulnerability classified under CWE-79 affecting Microsoft SharePoint Server Subscription Edition version 16.0.0. The vulnerability stems from improper neutralization of input during web page generation, which allows an authorized attacker with network access and privileges to inject malicious scripts into SharePoint web pages. This flaw can be exploited remotely without user interaction, enabling attackers to perform spoofing attacks that may lead to unauthorized disclosure of sensitive information, modification of data, or disruption of service. The vulnerability has a CVSS 3.1 base score of 8.8, indicating high severity, with attack vector network (AV:N), low attack complexity (AC:L), privileges required (PR:L), no user interaction (UI:N), and high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). Although no known exploits are currently reported in the wild, the vulnerability poses a significant risk due to the widespread use of SharePoint in enterprise environments for collaboration and document management. The lack of available patches at the time of publication necessitates immediate attention to mitigate potential exploitation. The vulnerability's exploitation could facilitate lateral movement within networks, data exfiltration, or further compromise of enterprise systems.

For European organizations, this vulnerability poses a substantial risk due to the extensive use of Microsoft SharePoint Server Subscription Edition in government, financial, healthcare, and industrial sectors. Exploitation could lead to unauthorized access to sensitive documents, intellectual property theft, and disruption of critical collaboration services. The ability to perform spoofing attacks may enable attackers to impersonate legitimate users or services, increasing the risk of social engineering and further compromise. Given the high confidentiality, integrity, and availability impacts, organizations could face operational downtime, regulatory penalties under GDPR for data breaches, and reputational damage. The network-based attack vector and lack of required user interaction increase the likelihood of successful exploitation in environments where privileged users access SharePoint services remotely or internally.

European organizations should implement a multi-layered mitigation strategy: 1) Monitor Microsoft’s security advisories closely and apply patches immediately once available. 2) Restrict SharePoint administrative and user privileges to the minimum necessary to reduce the attack surface. 3) Employ web application firewalls (WAFs) with custom rules to detect and block suspicious input patterns indicative of XSS attacks. 4) Conduct thorough input validation and sanitization on all user-supplied data within SharePoint customizations or extensions. 5) Enable logging and continuous monitoring of SharePoint access and anomalous activities to detect potential exploitation attempts early. 6) Educate privileged users about the risks of phishing and spoofing attacks that could leverage this vulnerability. 7) Segment SharePoint servers from other critical infrastructure to limit lateral movement in case of compromise. 8) Consider deploying Content Security Policy (CSP) headers to mitigate the impact of injected scripts. These measures, combined with rapid patching, will reduce the risk and potential impact of exploitation.