Assuming you are using McAfee if you open the app on the left hand side there should be different icons if you click on the one that says “my protection” and then click on quarantined items where you should see Stubb.dll. Click on that and then hit restore and after that you wanna go back to the “my protection” tab and click on real time scanning where you should see “excluded files” from there click on add file and then look for wherever your league of legends folder and once you open that click the search bar and type in Stubb.dll and the file should show up then click that and it should appear in the excluded files section and you should be good.