apt list --installed | grep firmware

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

bluez-firmware/oldstable,oldstable,now 1.2-3 all [installed]
firmware-amd-graphics/oldstable,oldstable,now 20161130-5 all [installed,automatic]
firmware-linux/oldstable,oldstable,now 20161130-5 all [installed]
firmware-linux-free/oldstable,oldstable,now 3.4 all [installed,automatic]
firmware-linux-nonfree/oldstable,oldstable,now 20161130-5 all [installed]
firmware-misc-nonfree/oldstable,oldstable,now 20161130-5 all [installed,automatic]
firmware-realtek/oldstable,oldstable,now 20161130-5 all [installed]