It's pretty much confirmed. Both the Allies and Russians discovered ghastly camps with piles of dead bodies. The numbers though, seem to get exaggerated with each passing year. When they censored Zundelsite - causing it to multiply around the world - I read it thoroughly, and he seemed to make a pretty good case - they simply did not have the capacity to dispose of, turn to ash, of the multiple millions claimed. It takes a certain amount of fuel/energy to turn a human body to ash. The nazis certainly disposed of many people, but the numbers claimed are doubtful. Most died of typhus and starvation. But how many?

To me it's a moot question. One million or 7 million. It was a lot, and there is no doubt the nazis intended to eradicate Jews from Europe.

Their final solution was extermination.

It's kinda like arguing about the numbers of Indians were eradicated in North America. The sheer numbers are exaggerated to multiply the outrage factor.

Millions seem most likely.