The Allowed threats page under Virus & threat protection in Windows Security shows a list of items that Windows Security has identified as threats, but that you have chosen to allow. Windows Security won't take any action against threats you've allowed.
If you have accidentally allowed a threat and want to remove it simply select it on the list, then select the Don't allow button. The threat will be removed from the list and Windows Security will once again act on it the next time it sees this threat.
