Airbus announced on November 28th that they "identified a significant number of A320 Family aircraft" that may be impacted by intense solar radiation, which could "corrupt data critical to the functioning of flight controls". Airbus recalled around 6,000 of these planes to fix the software required for flying.
On December 1st, Airbus announced that "the vast majority [of impacted planes] have now received the necessary modifications" and are ready to operate again.
Sources:
Airbus
Airbus