CVE-2026-77990 in Joomla Event Manager Extension
Summary
by MITRE • 08/27/2026
Joomla Extension - joomlaeventmanager.net - Attendee lists readable by any logged-in user in Joomla Event Manager < 5.0.1 - A non-manager can therefore read attendee names, usernames, registration dates and statuses for events they do not manage, including lists belonging to unpublished events.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 08/27/2026
The vulnerability identified within the Joomla Event Manager extension prior to version 5.0.1 represents a critical failure in access control logic that allows unauthorized data exposure. Specifically, this flaw enables any authenticated user who holds the role of an attendee or participant on one event to retrieve sensitive information regarding attendees of other events they do not manage and for which they have no legitimate authorization. This includes personal identifiers such as names and usernames, temporal data like registration dates, and operational statuses associated with those registrations. The severity is compounded by the fact that this access extends even to unpublished events, indicating a fundamental breakdown in how the application validates user permissions against specific event contexts rather than relying on broad or default allow-all policies for logged-in users.
From a technical perspective, this issue stems from improper authorization checks within the backend logic responsible for rendering attendee lists. When an authenticated session is established, the application fails to verify whether the current user possesses administrative privileges or explicit ownership of the target event before serving the requested data. Instead, it appears that the system relies on insufficient filtering mechanisms or exposes database queries without adequate row-level security constraints. This allows a malicious actor with minimal privileges to iterate through various event identifiers and extract comprehensive attendee databases for multiple events simultaneously. The ability to access unpublished event lists further suggests that the vulnerability bypasses standard visibility filters intended to restrict data from non-public entities, thereby exposing information that should remain strictly internal or hidden until an event is officially published.
The operational impact of this vulnerability is significant due to the potential for large-scale privacy violations and compliance failures. Attendee names and usernames constitute personally identifiable information (PII), while registration dates can be used to infer behavioral patterns or availability. In many jurisdictions, including those governed by the General Data Protection Regulation in Europe or various state-level privacy laws in the United States, the unauthorized disclosure of such data constitutes a serious breach requiring notification to affected individuals and regulatory bodies. Furthermore, attackers could leverage this information for targeted phishing campaigns, social engineering attacks, or credential stuffing attempts against specific users within an organization if those organizations use event registration as part of their internal communication infrastructure. The exposure of unpublished events also poses reputational risks, as it may reveal strategic plans or sensitive meetings that were intended to remain confidential until a later date.
This vulnerability aligns with CWE-284 Improper Access Control and CWE-601 URL Redirection to Untrusted Site 'Open Redirect' in the context of data exposure through improper validation, though more precisely it falls under CWE-862 Missing Authorization. In terms of offensive security frameworks, this behavior is consistent with ATT&CK technique T1530 Data from Cloud Storage Objects or T1005 Data from Local System depending on the specific implementation details, but primarily reflects a failure in role-based access control (RBAC) enforcement. To mitigate this risk, immediate action must be taken to upgrade the Joomla Event Manager extension to version 5.0.1 or later where these authorization checks have been corrected. Administrators should also audit their server logs for signs of automated scraping activity targeting attendee endpoints and consider implementing additional web application firewall rules that restrict bulk data retrieval from user-facing APIs until patches are applied. Regular security assessments focusing on access control logic across all modules are recommended to prevent similar vulnerabilities in other extensions or custom code within the Joomla environment.