And in a solar system already thought to host two others. Details:
The authors tested whether a system with planets in these apparent orbits would be stable, and it appears that it would be, provided none of the planets were much above their potential minimum masses. That would make most of them super-Earths, with the lone exception being an Earth-sized body.
Based on the brightness of GJ 667C, it’s possible to calculate where the potential habitable zone would reside around the star. On the inner edge of the zone, enough water enters the atmosphere that it reaches altitudes where the incoming stellar radiation can dissociate it, allowing the hydrogen to escape into space. GJ 667Cc is right at this boundary, but its high mass means that it might be able to retain water in the atmosphere despite the heat. GJ 667Cf is squarely within the habitable zone, while GJ 667Ce is further out, but still close enough that a healthy dose of greenhouse gasses like methane and carbon dioxide would warm it enough to keep water liquid.
All of these assumptions are based on the presence of an atmosphere and a reflectivity similar to that of Earth’s.
Those are some mighty big ifs.