Intel has announced that fourth and fifth generation Intel Core chips can now be patched up at the firmware level to prevent them from being affected by the Spectre exploit which has made vulnerable just about every CPU Intel has released since the mid '90s. Previously it had only released fixes for its latest-generation CPUs, but on Intel's Microcode update chart it has now green lit patches for Haswell and Broadwell chips too.
"Intel has completed all validation and is authorizing customers to use this MCU in a production environment," the chart confirms. That means that Haswell chips and Broadwell chips can now be protected. However, the status is in "production," which means that although Intel has done its part, the motherboard manufacturers now need to do theirs (thanks Hexus).
If you are running a Broadwell or Haswell chip -- with a "4" or "5" at the start of your Core CPU's part number -- then you need to keep an eye on your motherboard manufacturer's website, as it will hopefully have a BIOS update for you in the days to come. If your particular manufacturer has a BIOS flash utility you'll be able to use that to make the update. Otherwise you'll need to create a bootable USB drive and pop the new BIOS on there to make the firmware upgrade.
Although Windows updates will have provided you with a top-layer protection against the Spectre bug, you'll want to make sure you update your BIOS to protect your system properly when it becomes possible, as that will guarantee you're protected against the surprisingly powerful exploit route.