CVE-2025-9826 is a stored cross-site scripting (XSS) vulnerability identified in M-Files Corporation's Hubshare product prior to version 25.8. This vulnerability arises from improper neutralization of input during web page generation, classified under CWE-79. Specifically, authenticated attackers can inject malicious scripts that are stored by the application and subsequently executed in the browsers of other users who access the affected content. The vulnerability requires the attacker to have some level of authenticated access (low privileges) and involves user interaction (victims must view the malicious content). The CVSS 4.0 score of 7 (high severity) reflects the network attack vector, low attack complexity, no privileges required beyond authentication, and partial impact on confidentiality and integrity, with high impact on confidentiality. The vulnerability does not require user privileges beyond authentication but does require user interaction to trigger the malicious script execution. No known exploits are currently reported in the wild, and no patches have been linked yet. Stored XSS vulnerabilities can lead to session hijacking, credential theft, unauthorized actions on behalf of users, and potential pivoting within the affected environment. Given Hubshare’s role as a collaboration and file-sharing platform, exploitation could compromise sensitive business data and user accounts.

For European organizations using M-Files Hubshare, this vulnerability poses a significant risk to confidentiality and integrity of sensitive information shared via the platform. Attackers exploiting this flaw could execute arbitrary scripts in the context of other users’ sessions, potentially leading to data theft, unauthorized access, and manipulation of shared documents or collaboration workflows. This could disrupt business operations, damage trust, and lead to regulatory non-compliance, especially under GDPR requirements for protecting personal data. The requirement for authenticated access somewhat limits the attack surface but does not eliminate risk, as insider threats or compromised accounts could be leveraged. The stored nature of the XSS means that malicious payloads persist and can affect multiple users over time, increasing potential damage. European organizations with extensive collaboration and document sharing needs are particularly vulnerable to data leakage and operational disruption from such attacks.

Organizations should prioritize upgrading M-Files Hubshare to version 25.8 or later once available, as this will likely contain the official patch. Until then, practical mitigations include: 1) Implementing strict input validation and output encoding on all user-generated content within Hubshare to prevent script injection; 2) Employing Content Security Policy (CSP) headers to restrict execution of unauthorized scripts in browsers; 3) Restricting user permissions to the minimum necessary to reduce the risk of malicious input from low-privilege users; 4) Monitoring and auditing user-generated content for suspicious scripts or payloads; 5) Educating users about the risks of clicking on unexpected or suspicious links within the platform; 6) Using web application firewalls (WAFs) with rules tuned to detect and block XSS payloads targeting Hubshare; 7) Enforcing multi-factor authentication to reduce the risk of account compromise that could facilitate exploitation. These steps, combined with timely patching, will reduce the risk of exploitation and limit potential damage.