Both Westfield and Brookfield are still open, but hours have been reduced as follows–
Westfield: 11a to 7p on Mondays through Saturdays and noon to 6 on Sundays
Brookfield: 11a to 6p

After a stroll through both malls, I would say stores are about half open (excluding the restaurants, which of course are all closed). It was still eerie, and even the Brookfield birds seemed rattled.

The pharmacies are definitely open, as is Le District, but you can only access it through the outside doors on Liberty Street. (I bought myself a fancy bottle of French hand soap, figuring might as well enjoy those 20 seconds 50 times a day.)

Hours are likely to change day by day, so you are headed down, check the Westfield or Brookfield websites. You can also find the list of open stores in Hudson Square here, compiled by the BID. And as a side note, Hudson Yards has closed its retail operations entirely.