The Proctorio Secure Exam Proctor Chrome extension version 1.5.25220.33 contains a vulnerability identified as CVE-2026-2345, classified under CWE-346 (Origin Validation Error). The extension uses multiple window.addEventListener('message', ...) handlers to facilitate internal communication. However, these handlers fail to properly validate the origin of incoming postMessage events. Specifically, the extension processes messages based solely on the presence of a fromWebsite property within the message payload, neglecting to verify the event.origin attribute, which is critical for ensuring messages come from trusted sources. This improper origin validation can allow a malicious website or attacker-controlled page to send crafted messages to the extension, potentially triggering unintended behaviors or leaking sensitive information related to the exam environment. The vulnerability has a CVSS 3.1 base score of 3.6, indicating low severity. The attack vector is local (AV:L), meaning the attacker must have local access to the victim's browser environment, and the attack complexity is high (AC:H), requiring specific conditions or user interaction (UI:R). No privileges are required (PR:N), so any user can be targeted. There are no known exploits in the wild at this time, and no patches have been published yet. Given the extension's role in securing online exams, any manipulation or information leakage could undermine exam integrity or privacy. The vulnerability primarily impacts confidentiality and integrity but does not affect availability. The issue highlights the importance of strict origin validation in browser extension messaging to prevent cross-origin attacks and unauthorized message injection.

For European organizations, particularly educational institutions relying on Proctorio for secure online examinations, this vulnerability poses risks to the confidentiality and integrity of exam processes. An attacker who can lure a user to a malicious website or inject scripts in the browser context could exploit the origin validation flaw to send unauthorized messages to the extension. This could lead to leakage of exam-related data or manipulation of the extension's behavior, potentially compromising exam fairness or privacy. Although the attack requires local access and user interaction, the widespread use of Proctorio in European universities and certification bodies increases the attack surface. The impact is mitigated by the high attack complexity and lack of known exploits, but the sensitive nature of exam environments means even low-severity vulnerabilities warrant attention. Disruption or data leakage could damage institutional reputation and trust in online assessment platforms. Additionally, regulatory frameworks like GDPR emphasize protecting personal data, so any leakage could have compliance implications.

Organizations should monitor Proctorio vendor communications for patches addressing this vulnerability and apply updates promptly once available. Until a patch is released, users should be advised to avoid visiting untrusted websites during exam sessions to reduce the risk of malicious message injection. Security teams can audit browser extension configurations and restrict extension permissions where possible. Developers and administrators should advocate for or implement strict origin validation in all message event handlers, ensuring event.origin is checked against a whitelist of trusted domains before processing messages. Employing browser security features such as Content Security Policy (CSP) can help limit exposure to malicious scripts. User education is critical to prevent social engineering that might lead to exploitation. Finally, institutions should consider layered security controls around exam environments, including network segmentation and endpoint protection, to reduce the likelihood of local attacker presence.