It shows it is crashing but the issue why is that your Video Card Drivers need to be updated.

See if you can find updates for your Intel(R) HD Graphics as they are A not old : 4-7-2017 You can Google Intel(R) HD Graphics and find the download page https://downloadcenter.intel.com/product/80939/Graphics-Drivers, but you may have to know what generation chipset you are using. CPU-Z would tell you this https://www.cpuid.com/

Can also try : https://www.intel.com/content/www/us/en/support/detect.html

Note: I do see a few errors in the drivers.  Old & corrupted Drivers cause a wide range of issues. Please keep them updated to prevent issues and you never know when Intel will stop supporting them.

Note : you maybe running the wrong drivers if did not check against your chipset.

hi, please try this: go to the firefox menu ≡ > options > privacy & security panel and under permissions check the setting to prevent accessibility services from accessing your browser.

edit: also what kind of device / model is the crashing machine?

Thank you for your replies. I decided to take the coward's way out for now and go back to 56.0.2., which works for me. I know that's only a temporary measure, so I'll definitely look at your suggestions when I give 57 another try.

Re the graphics, I did update the driver a few days ago (while running 57), and it is up to date according to the Intel Drive & Support Assistant. My desktop computer was built by a local computer shop.