Registry values not cleaned up on exit via power button — Windows power options permanently disabled

[Sub2Nex]

Bug Report

Title: Registry values not cleaned up on exit via power button — Windows power options permanently disabled

Describe the bug

When closing SEB using the integrated power button (with or without a quit password), the NoClose registry value is intermittently not deleted after SEB exits.

This causes Windows to permanently hide the power/energy options from the Start Menu and taskbar. The restriction survives reboots since the value is written to the persistent machine and user registry hives.

To Reproduce

1. Launch SEB with any config (password-protected quit or confirmation-only).
2. Close SEB using the integrated power button in the SEB taskbar.
3. After SEB fully exits, open regedit and check for NoClose (DWORD 1) in:
   • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
   • HKEY_USERS\<SID>\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
4. Reboot the machine.
5. Observe: Windows power/energy options are still missing from the Start Menu and taskbar after reboot.

Expected behavior

All registry values set during an exam session are fully reverted on exit, regardless of how SEB is closed.

Actual behavior

The NoClose DWORD persists permanently in the registry after exit. Power/energy options remain hidden even after rebooting. The only resolution is manually deleting the value via regedit.

Workaround

Manually delete NoClose from:

• HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
• HKEY_USERS\<SID>\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer

Environment

• OS: Windows 10 / 11
• Reproducibility: Intermittent — more likely when the Explorer\Policies subkey did not already exist before SEB launched

Additional context

The issue appears to be in the lockdown feature configuration restore/cleanup path (SafeExamBrowser.Lockdown). Specifically, MachinePowerOptionsConfiguration and UserPowerOptionsConfiguration silently fail to revert their changes on shutdown under certain registry key states.

[dbuechel]

Thank you very much for the extensive report. We have received similar reports in the past, but could up and until now not pin down the issue. We'll definitely thoroughly investigate your findings from above and report back once we know more.

[dbuechel]

Thanks again for the report. I have meanwhile been trying to reproduce the issue, but have most unfortunately repeatedly failed to do so - not only on one single, but on two Windows 11 and one Windows 10 machine. Also the existence resp. absence of the ...\Policies\Explorer subkey did unfortunately not cause the issue to arise.

Could you thus please provide the log files of the affected session(s)? And are there any further circumstances or factors which you have observed that could potentially influence the situation and cause the issue to arise?

[github-actions]

This issue is stale because it has been open for 28 days with no activity. It will soon be closed automatically if there are no updates.