After updating Windows, I suddenly can't type the left square bracket character ([) with my physical keyboard. The right bracket (]) and every other key work normally. I installed the following updates beforehand: the August 2026 .NET Framework Security Update (KB5120710), the August 2026 Security Update (KB5121003, build 26100.9168), and the Windows Malicious Software Removal Tool x64 version 5.144 (KB890830). Could one of these updates have caused the problem, and what troubleshooting steps should I try? Is it possible to uninstall or roll back the updates safely?
3 Answers
You can review and remove recent updates under Settings > Windows Update > Update history > Uninstall updates. However, uninstalling security updates should be a later troubleshooting step, since the on-screen keyboard test can help determine whether the problem is hardware-related first.
This is probably a coincidence rather than an update problem. A single key failing while the rest of the keyboard works often points to a physical keyboard issue, a stuck key mechanism, or a connection problem. You can try reconnecting the keyboard or testing another one before rolling back security updates.
Open the Windows on-screen keyboard by pressing Win+R, entering osk.exe, and pressing Enter. If the left bracket works there, Windows can generate the character and the issue is likely limited to the physical keyboard or its connection. Since the virtual keyboard works, reconnecting or replacing the physical keyboard is worth trying.
The left bracket does work with the on-screen keyboard. I also replugged the physical keyboard, and its drivers are already up to date, so I’m testing whether removing the recent updates changes anything.
I found the uninstall option and can remove two of the listed updates. I’ll check whether that makes any difference.