CVE-2026-45128 PUBLISHED

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 set_default 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/functions_view_manager.php. This issue is fixed in version 1.8.40.

• https://github.com/mybb/mybb/security/advisories/GHSA-m6hr-25cj-p58q
• https://github.com/mybb/mybb/commit/736a2bcbc7cc104df8ae6c0a160aa3917a1ceec0
• https://github.com/mybb/mybb/releases/tag/mybb_1840
• https://mybb.com/versions/1.8.40

• CWE-352: Cross-Site Request Forgery (CSRF) CWE