Scammers are actively exploiting a bug in Firefox that causes the browser to lock up after displaying a message warning that the computer is running a pirated version of Windows that has been hacked. The message, which appears without any any user interaction upon visiting a site, reads: Please stop and do not close the PC \u2026 The registry key of your computer is locked. Why did we block your computer? The Windows registry key is illegal. The Windows desktop is using pirated software.