Decade-old Microsoft Secure Boot flaw exposed via unrevoked legacy shims

A long-standing vulnerability in Microsoft's Secure Boot system has gone undetected for approximately ten years. The flaw stems from old 'shim' files — small bootloader components — that Microsoft neglected to revoke after they became obsolete. These forgotten shims can be exploited to bypass Secure Boot protections, a feature designed to prevent unauthorized software from loading during system startup. Security researchers have now identified the oversight, raising concerns about the integrity of boot-level security on affected systems.