KB5087544

Microsoft has released cumulative update KB5087544 for Windows 10, version 22H2 as part of the May 2026 Patch Tuesday for devices enrolled in the Extended Security Updates (ESU) program.

• Secure Boot. The update includes dynamic display of Secure Boot status in the Windows Security app. As part of the Windows quality update, additional data has been added to accurately identify compatible devices. This expands the list of devices that can automatically receive new Secure Boot certificates. Certificate installation occurs in stages — only on devices where successful updates have been recorded, ensuring controlled deployment.
• Daylight saving time. An update for the Arab Republic of Egypt is included, supporting the daylight saving time changes introduced by the government in 2023.

Known issues: RDP security warnings — the Remote Desktop Connection security warning dialog box might have displayed incorrectly in multi-monitor configurations with different display scaling settings. This issue could occur after installing the Windows security update released on April 14, 2026 (KB5082200).

Cumulative update KB5087544 for PCs is installed automatically via Windows Update. To check, go to Settings > Update & Security and click Check for updates. A system restart is required to complete the installation. After the update, the Windows 10 (version 22H2) build number will change to 19045.7291.

How the new features work:

Secure Boot: The mechanism dynamically reads the UEFI Secure Boot status via a secure variable storage API. During the update, Windows verifies the signature of new certificates using VerifyTrust() and matches TPM registers (TCG_LOG) against reference values. Deployment is staged: a certificate is added to the db (signed key) only after successful verification on a subset of devices, preventing incorrect boot.

Daylight saving time: The update modifies the time zone rule base in the registry (HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones) and in tzres.dll — a resource containing offset information. The Windows Time Service (W32Time) recalculates daylight saving time transitions for Egypt starting from 2023, syncing with UTC via NTP servers. Changes apply without reboot but require updating the timezone.sdf file.

Known issues: RDP security warnings: When using multiple monitors with different scaling (dpiAwareness = PerMonitorV2), the MessageBox() function in mstscax.dll miscalculates the RDP security warning dialog coordinates. This happens because GetSystemMetrics() returns incorrect values due to mixed DPIs. The issue occurs after installing KB5082200, affecting RDP protocol version 8.1 and above.

The last 10 Windows updates: