While descending with no weather return indication on the weather radar and breaking out of a scattered undercast layer the flight path was exposed to a single cloud. PF immediately reduced the speed and PM requested a weather deviation. 3-4 seconds of cloud passage created up and down drafts effect which caused some cabin crew injuries. The flight encountered moderate turbulence with a G-load change of +2.2 experienced for several seconds before returning to a steady flight condition The Autopilot remained engaged and all parameters remained within the aircraft limitations. The flight crew checked the cabin status and were informed by the senior cabin crewmember that one cabin crewmember, located in adjacent to the upper right door (UR1) area, was injured and was unable to perform further duties. The injured cabin crewmember was moved to a passenger seat for the remainder of the flight. The flight continued to the destination and landed normally. Following a medical examination, the injured cabin crewmember was confirmed as having sustained a fracture to the right ankle. Nine other cabin crewmembers reported minor injuries.