http://www.newsweek.com/nasa-and-russian-space-agency-tight-lipped-source-space-station-air-leak-1120153

In late August, air started bleeding from a Soyuz spacecraft docked to the International Space Station. Astronauts isolated and plugged the small leak quickly, but rumors surrounding its cause have been harder to contain.

Micro-meteorites, manufacturing defects and even astronaut sabotage have all been touted as potential, and controversial, reasons for the leak. As investigations continue, NASA and Russian space agency Roscosmos are keeping tight-lipped.