Some Dell XPS 15 9560 laptops are experiencing a severe BIOS related HDMI problem
addresses the Intel security advisories INTEL-SA-00185 and INTEL-SA-00191.
It also should fix a Secure Boot Option ROM Signature Verification issue and a separate keyboard backlight issue. BIOS 1.14.2 also brings support for the Dell Dock Station WD19 to the XPS 15 9560. However, Dell did not inform people that the update may also break HDMI for some machines.
Perhaps engineers somehow missed this during testing, but this seems like a glaring bug to have overlooked. Dell first released BIOS 1.14.2 on April 25, which it labels as an urgent update on its support page. Since then, there have been multiple reports on Dell Support and Reddit of BIOS 1.14.2 rendering HDMI ports unusable on XPS 15 9560 machines.
It took until yesterday before a Dell Community Manager responded, who advised and stated the following:
I've forwarded your concerns over to the Engineers. In the meantime, BIOS update 1.14.2 is a security update and does not affect the HDMI, you can continue to use 1.12 until we have more information.
While this seems a simple, albeit frustrating, workaround for the time being, several people have reported that rolling back to BIOS 1.12.1 causes further issues. Some people have stated that not all firmware packages are restored during the rollback process, which has caused "random BSOD in Windows 10 and Kernel panic in Linux" for one person. In short, rolling back to BIOS 1.12.1 may fix the HDMI problem for some machines, but it may cause further issues for others, which will only compound frustrations.
Unfortunately, we have no other information at this stage and are awaiting further comment from Dell. As always, let us know in the comments if you have experienced this issue with your XPS 15 9560 and if you found any other workarounds or solutions.