The Geo Block product is not to be used as a 100% blocking system for visitors from particular locations.
If someone really want's to access your site, they can. Hence it should only be used for blocking majority of the general public.
How can visitors from a blocked location access your site?
Using a VPN
A VPN is service that let's your browse the internet from a selected location around the world. There are plenty of VPN services available for anyone to use and to access the internet from a country or location of their choice.
It is easily possible for a visitor to use a VPN to access your site from a location not on your blocked list.
We don't have a way to detect VPN connections at the moment.
It is also possible to download browser plugins or software that can block a particular script from executing on your site. Hence it is possible a visitor can stop our Geo Block from executing, thus gaining access to your site.