CVE-2026-1011 is a stored cross-site scripting (XSS) vulnerability identified in the Altium 365 platform, specifically within the Support Center's AddComment endpoint. The root cause is the lack of server-side input sanitization, allowing attackers to submit malicious HTML and JavaScript payloads via modified POST requests. Although the client interface applies HTML escaping, this is insufficient because the backend stores the raw input, which is then rendered verbatim when support cases are accessed by other users, including support personnel with elevated privileges. This results in arbitrary script execution in the victim's browser context, enabling attackers to perform actions such as session hijacking, credential theft, or executing malicious operations within the scope of the user's session. The vulnerability does not require authentication but does require user interaction to trigger the malicious script. The CVSS v3.1 score of 8.2 reflects a high severity, with network attack vector, low attack complexity, no privileges required, but user interaction needed, and a scope change due to impact on other users. While no public exploits are currently known, the vulnerability poses a significant risk given the sensitive nature of support case data and the elevated privileges of some users who may be targeted. The vulnerability is categorized under CWE-79 (Improper Neutralization of Input During Web Page Generation) and CWE-116 (Improper Encoding or Escaping of Output).

For European organizations, this vulnerability could lead to unauthorized access to sensitive technical support information, intellectual property, and potentially internal credentials if exploited. Since support staff with elevated privileges can be targeted, attackers might leverage this to escalate privileges or pivot within the organization’s network. The confidentiality impact is high due to potential data leakage, while integrity impact is limited but non-negligible as attackers could inject misleading or malicious content into support cases. Availability impact is minimal. The exploitation ease is relatively high given the lack of required privileges and the network attack vector, but user interaction is necessary. Organizations relying on Altium 365 for electronics design and support management could face operational disruptions and reputational damage if attackers exploit this vulnerability to compromise internal communications or steal sensitive data.

1. Apply official patches or updates from Altium as soon as they become available to address the vulnerability at the source. 2. Implement strict server-side input validation and sanitization to reject or neutralize any HTML or JavaScript content submitted via the AddComment endpoint. 3. Employ robust output encoding/escaping on all user-generated content before rendering it in browsers to prevent script execution. 4. Restrict access to support case views to only necessary personnel and enforce least privilege principles. 5. Monitor logs and user activity for unusual behavior indicative of XSS exploitation attempts. 6. Educate support staff about the risks of clicking on suspicious links or interacting with unexpected content within support cases. 7. Consider deploying web application firewalls (WAFs) with rules designed to detect and block XSS payloads targeting the affected endpoints. 8. Conduct regular security assessments and penetration testing focused on web application input handling and output rendering.