If you encounter the above error when attempting to download and/or install LockDown Browser, then it's likely Windows Defender interfering. To work around the problem, open Windows Defender on your computer and start by disabling "Virus & Threat Protection" only. If the problem persists, then also disable other components of Windows Defender, including:

* Firewall & Network Protection
* App & Browser Control

After the install successfully completes, you should re-enable all components of Windows Defender that you may have disabled.