User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:61.0) Gecko/20100101 Firefox/61.0 Build ID: 20180705213349 Steps to reproduce: 1) Load "http://couldformonths.tk", or "http://couldformonths.tk/?number=855-257-7118" in a new tab. 2) Reload page if necessary to bring-up "Authentication Required" window. 3) Close "Authentication Required" window. 4) Congratulations! Firefox Quantum has been hijacked! Enjoy the repeating audio message threatening to disable your windows computer. Call the toll-free number immediately! Actual results: 1) "Block pop-up windows" has failed to block the "Authorization Required" pop-up. 2) Firefox fails to allow window focus to be removed from pop-up window. 3) Firefox fails to block "Authorization Required" window from re-opening when closed. 4) Firefox fails to allow the user to close the tab with the offending web site. Expected results: Firefox developers should have considered more carefully the security implications of failing to respond to a window focus event, which prevents the user from closing the tab with the offending website.