Windows computers face an important security deadline this Thursday, 26 June 2026. The Secure Boot certificates shipped in every Windows PC since 2011 are expiring, and Microsoft has been rolling out replacements through Windows Update.

• What it is: Secure Boot is a feature that runs before Windows loads, verifying that only trusted software starts on your PC. The certificate underpinning this trust expires on 26 June 2026.
• Who is affected: Any Windows PC that has not received recent Windows updates. Businesses with unmanaged or infrequently updated devices are most at risk.
• What happens if you miss it: PCs without the updated certificate will keep running normally, but will stop receiving security protections for the boot process. This makes them more vulnerable to boot-level malware, and future Windows upgrades may fail.
• What to do: Ensure all Windows devices have applied the April 2026 or later Windows Update. In Windows Security, check Device Security to confirm Secure Boot status shows the new 2023 certificates. If any device shows the old certificates, run Windows Update immediately.

If you manage multiple devices, we recommend auditing all PCs for update status before the end of this week. Microsoft's guidance has full details on how to verify your status.