When I say our current knowledge, I mean fundamental concepts like math, physics, chemistry etc. It’s not like if aliens are proven to exist that 1+1 won’t equal 2. Most of the sciences that will be challenged are sciences that are mostly theoretical like astrophysics.
The fundamental concepts of physics would likely change, because under those fundamental concepts there's virtually no way they could even arrive here without violating what we know about the laws of physics.
The fundamental concepts of biology would likely change too, because interacting with beings from another planet for the first time ever would almost certainly upend much of what we know.
If any of the many ridiculous claims about their spacecrafts' special powers are true, then that would also violate physical law and completely change those fields of physics and engineering.
If our governments really have known about them and were recovering crafts or communicating with them in any way, then the entire last century of history and politics would change, and absolutely everything would be re-evaluated in that light (including the fact that we can't imagine how such a coverup would be remotely possible with what we currently understand of politics).
And then just look right above where people want to give them telepathy, that would completely change everything we know of physics and biology as well.
