If gravity can leak out of our universe, is it possible gravity is leaking into our universe in a similar manner, causing effects attributed to dark matter?

Cosmologists have no evidence whatsoever that gravity — or anything else, for that matter — can “leak” out of, or into, our universe. The universe is everything around us, including parts of it that are so far away, we will never be able to see them. While it is possible for an object to be beyond our observable horizon — farther away than about 50 billion light-years — we don’t know, even in principle, how something could be beyond our universe.