10fastfingers.com

Where shall I mail to report a game bug? Thanks.

If you want to mail the site admin you can do so under "Contact" up to the right on the 10fastfingers test and competition page. You can also write a suggestion under "Feedback" located in the same place, but this will probably be less effective. Other than that you have the option to write a post describing the bug in the forum. There's a good chance it has already been reported here, and that the bug is known. The site admin will probably only try to fix the bug if you know exactly how it occurs. Without access to the source code it can be very difficult to figure that out.

The problem is that the bug is exploitable, to overpass certain WPM, so I will contact him through mail.
Thank you for your prompt answer.