CVE-2026-45128: MyBB: ACP Users View Manager default CSRF
MyBB is free and open source forum software. Prior to 1.8.40, the ACP Users View Manager module does not validate requests correctly, allowing same-site attackers to change a victim administrator's default user list view by embedding a specially crafted URL. The Set as Default control named setdefault in Admin CP, Users & Groups, Users, View Manager changes the administrator's default view on GET requests without request forgery protection. The uniquely identifying implementation details include Users & Groups → Users → View Manager, and admin/inc/functionsviewmanager.php. This issue is fixed in version 1.8.40.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
MyBB (ACP Users View Manager CSRF)to a version that resolves this vulnerability.Fixed in 1.8.40
Event History
Frequently Asked Questions
Which deployments and users are exposed?
MyBB installations running versions before 1.8.40 are affected if an administrator uses the Admin CP Users View Manager. The issue changes only that administrator's default user-list view.
What is required to exploit the issue?
An attacker needs to get a victim administrator to load a specially crafted URL from the same site. The vulnerable action is performed through a GET request and does not require request-forgery protection.
What is the available fix?
Upgrade MyBB to version 1.8.40, which fixes the request validation for this action.