Oumuamua was not an alien probe into the Solar System (probably)

 

Ever since the strange object Oumuamua was sighted after passing through the Solar System and headed out, there have been several different theories about what it actually was (because it was clear that it was unusual).  The theories covered the range from an interstellar comet to a Rendesvous with Rama-type probe that was sent to check us out from some far distant star system (by intelligent entities). 

A more plausible theory has been put forth;  that it was a chip off a planet like Pluto.

Interstellar object 'Oumuamua is a pancake-shaped chunk of a Pluto-like planet

Oumuamua was like a comet in some respects, but

"However, if 'Oumuamua was a comet, it was unlike any previously seen in the solar system. It lacked any detectable escaping gas, unlike the big tails typically spotted streaming from comets. In addition, its shape — resembling either a cigar or a pancake — was unlike any known comet. Moreover, the rocket-like push seen from 'Oumuamua was stronger than what researchers expected from comets."

So, this is what they think now:

"These new findings suggest 'Oumuamua was shaped more like a pancake than a cigar. It may also be smaller than previously thought — just 147 by 144 by 24 feet (45 by 44 by 7.5 meters) in size when astronomers first detected it. In comparison, prior estimates suggested 'Oumuamua was about 1,300 feet (400 m) long."

So, still unusual, and still interstellar.  But we're probably safe from aliens (for now).