Microsoft has alerted users that Secure Boot certificates will begin to expire in June, affecting most Windows devices. Users must update these certificates to avoid disruptions, as failing to install the latest Windows update could prevent devices from booting securely. A "one-time restart" will be required after the update to load new certificates. If the update is not installed by June 1, users may see a red stop icon in the Windows Security app. The update issued on May 12 was modified on May 15 to warn that it might fail to install. Microsoft indicates that most users will need to restart their PCs, although this may revert the update. The latest updates will expand the number of devices eligible for new Secure Boot certificates, but users are uncertain about how many PCs will be affected due to a phased rollout approach.