BIOS 1.17.2 can be directly downloaded from Dell's support site here.  Please note as per the release notes, once this update is applied you might not be able to downgrade back to 1.16.2. 
Hello,Me and my colleagues noticed that there is a newer version of our Latitude 7420 laptop BIOS firmware, but we are confused from the info that comes with it. The latest version from the day before yesterday is 1.17.2 and here is what the info from the download portal is:"Important Information - Once the BIOS is upgraded, you cannot downgrade the BIOS EXE/Recovery (RCV) to versions earlier than 1.17.1. BIOS downgrades are restricted when there are security updates and important fixes with earlier versions that impact the functionality of the system."But the most recent and earlier version uploaded in the download portal is 1.16.2. So it seems that if we encounter a problem, we can't downgrade to it?Thank you.
Confused with Latitude 7X20 newest BIOS