Had a virus come in with a download: SoftwareBundler:Win32/ICLoader.D some weeks ago.
Not a problem - Defender caught it - either I or Defender removed the relevant files - I forget which - including from Recycle Bin.
In any event, having done many scans since, results always show no threats found.
If I select "Scan History" I see "No Current Threats". Under Quarantined Threats or Allowed Threats, I select "See Full History" and I always get one item. I click Clear History, get prompted for an admin acct password, the list appears to disappear, then re-appears - link a "blink".
Once in a dozen times, the interface dies. Have rebooted many times. Have tried clearing from an admin acct directly. Results are always the same.
Scans are show not threats. System behaves normally.
Tempted to look for where the Defender history is kept - have not found it in Registry. I do not want to take ownership of system files/folders to go poking around. Windows 10 makes it very hard for somebody to help themselves or even to learn without risking their system's integrity.