Are quasars dangerous?
Not to us.
The closest quasar to Earth is about 2,000 light years away. So despite the fact that it put out around 1,000,000,000,000 times as much energy as the sun, it is simply too far away to be dangerous.
Quasars are very distant objects which emit energy at they rate of billions of that of the sun.
A quasar is the supermassive black hole at the centre of a galaxy which is consuming vast amounts of material.
Our galaxy has a supermassive black hole at its centre. There is not enough material to feed it to make it a quasar.
Even if the centre of our galaxy was a quasar it is so far away (26,000 light years) that it wouldn't have a significant effect on the radiation the Earth receives.