Comment 14 for bug 1572659

Experienced the same. WIFI no longer working after upgrading on Dell XPS 13 9343 to Ubuntu 16.04 LTS.

SecureBoot is enabled (and will remain so)

lspci -nnk | grep 0280 -A2
02:00.0 Network controller [0280]: Broadcom Corporation BCM4352 802.11ac Wireless Network Adapter [14e4:43b1] (rev 03)
 Subsystem: Dell BCM4352 802.11ac Wireless Network Adapter [1028:0019]
 Kernel modules: bcma, wl

sudo lshw -C network
  *-network UNCLAIMED
       description: Network controller
       product: BCM4352 802.11ac Wireless Network Adapter
       vendor: Broadcom Corporation
       physical id: 0
       bus info: pci@0000:02:00.0
       version: 03
       <snip>