Cosmonauts cleaning the ISS's windows and sensors claim to have found sea plankton.
On the outside.
On the freaking OUTSIDE.
NASA is remaining mum on the subject and says it's not confirmed and I'm only seeing it in UK sources, but if so...the question is not so much how it survived (tardigrades can survive in vacuum for days) as how the heck it got there.
And if this is real, then it's one piece of evidence for biological contamination between and beyond planets.
Or it's all a hoax. No way of knowing yet.