Some of these exploits can be used in a browser. They leave no trace. So it is hard to tell how much these exploits have been used in the past and how likely a

Some of these exploits can be used in a browser. They leave no trace. So it is hard to tell how much these exploits have been used in the past and how likely a wider attack will happen in the future. Some of these exploits have been used in targeted attacks towards end users so the risk is not 0.